1 Copyright © [2012]. Roger L. Costello. All Rights Reserved. XML Schema 1.1 Roger L. Costello 14 December 2012 Structure Specification:

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Copyright © [2012]. Roger L. Costello. All Rights Reserved.

XML Schema 1.1

Roger L. Costellohttp://www.xfront.com

14 December 2012Structure Specification: http://www.w3.org/TR/xmlschema11-1/Datatype Specification: http://www.w3.org/TR/xmlschema11-2/

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Acknowledgements

• Special thanks to Michael Kay and Michael Sperberg-McQueen for answering my endless questions.

• Thanks to the following people for their suggestions and identifying typos:– Noah Mendelsohn– Mukul Gandhi– Pete Cordell– Ken Starks– Dave Peterson– Fraser Goffin– Paul Jones– Henry Callihan

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XSD 1.1 is a Recommendation

• XML Schema 1.1 became a standard on April 5, 2012 (the W3C calls it a “recommendation” not a standard, but they are the same)

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The "Big Picture"

• I created another tutorial:XML Schema 1.1 for Managers

• I strongly recommend reading it prior to reading this.

• It will give you the "big picture."

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Prerequisite

• This tutorial assumes you already have a thorough understanding of XML Schemas 1.0*

• Also, you should have a pretty good understanding of XPath. Ideally you know XPath 2.0

* See my tutorial on XML Schema 1.0: http://www.xfront.com/xml-schema.html

You don't know XPath?No problem! I've created aQuick Intro to XPath. Seequick-intro-to-xpath.ppt

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Viewing this Tutorial

• This tutorial is best viewed in slide show mode– Under the View menu select Slide Show

• Periodically you will see an icon at the bottom, right of the slide indicating that it is time to do a lab exercise. I strongly recommend that you stop and do the lab exercise to obtain the maximum benefit from this tutorial.

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Your 1.0 Schemas will still work

An instance document conforming to a 1.0 schema can be validated using a 1.1 validator, but an instance document conforming to a 1.1 schema may not validate using a 1.0 validator.

XML Schema 1.0

XML Schema 1.1

XML Schema 1.1 is a superset of XML Schema 1.0

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Namespaces for 1.1

Same as in 1.0

http://www.w3.org/2001/XMLSchema

Use this namespace in your schema:

http://www.w3.org/2001/XMLSchema-instance

Use this namespace in your instance document:

Example: with regard to namespaces this 1.1 schema looks identical to a 1.0 schema:

<?xml version="1.0"?><xs:schema

xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> …

</xs:schema>

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New namespace in 1.1

XML Schema 1.1 introduces a new namespace, the version control namespace:

http://www.w3.org/2007/XMLSchema-versioning

Note: the convention is to use "vc" as the namespace prefix,e.g. vc:typeAvailable.

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XML Schema 1.1 Validators

• The schema-aware version of SAXON (version 9.3 or later) supports the full XML Schema 1.1 specification: http://www.saxonica.com/

• Apache XERCES-J (version 2.11.0 or later) supports XML Schema 1.1: http://xerces.apache.org/xerces2-j/

• You can create XML Schema 1.1 schemas today!

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Running SAXON from Oxygen XML

Select "Preferences" in this menu. It will open the dialog box shown here. Then select the 1.1 radio button. Then press the OK button. Now, when you click on Saxon-EE your XML document will be validated using a 1.1 schema validator.

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5 minute intro

Summary of Changes to the Structures Specification: http://www.w3.org/TR/xmlschema11-1/#changesSummary of Changes to the Datatypes Specification: http://www.w3.org/TR/xmlschema11-2/#changes

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The <assert> Element

The <assert> element is used to make assertions about element and attribute values. An assertion may state a relationship, such as "A meeting's end time must be greater than its start time," or an assertion may state a constraint on an element or attribute above and beyond the constraint specified by its declaration.

Example: the Publisher element is declared to be of type string, but the assertion constrains it to just two string values, 'Wrox Press' and 'McMillan Publishing':

<element name="Book"> <complexType> <sequence> <element name="Title" type="string" /> <element name="Author" type="string" /> <element name="Date" type="string" /> <element name="ISBN" type="string" /> <element name="Publisher" type="string" /> </sequence> <assert test="(Publisher eq 'Wrox Press') or (Publisher eq 'McMillan Publishing')"

/></complexType></element>

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The <assertion> Facet

The <assertion> facet is used to constrain simpleTypes. $value is a built-in variable holding the value of the simpleType.

Example: the Evens simpleType has the even numbers from 0 to 100:

<simpleType name="Evens> <restriction base="integer"> <minInclusive value="0" /> <maxInclusive value="100" /> <assertion test="$value mod 2 = 0" /> </restriction></simpleType>

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The <alternative> Element

The <alternative> element is used to provide an element a choice of types, the actual type used in an instance document depends on the value of attributes.

Example: if the value of the kind attribute is 'book' then <Publication>'s type is BookType; if the value of the kind attribute is 'magazine' then its type is MagazineType; otherwise, its type is PublicationType.

<xs:element name="Publication" type="PublicationType"> <xs:alternative test="@kind eq 'book'" type="BookType" /> <xs:alternative test="@kind eq 'magazine'" type="MagazineType" /></xs:element>

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The xs:error Datatype

The error datatype is used to trigger an error. It may be used wherever a type is used.

Example: continuing with the last example, suppose PublicationType is declared in a schema that cannot be modified, and it declares the kind attribute to be of type string. In your schema you want the value of kind to be restricted to 'book' and 'magazine.' Here's how to throw an error if kind does not have the value ‘book’ or ‘magazine’:

<xs:element name="Publication" type="PublicationType"> <xs:alternative test="@kind eq 'book'" type="BookType" /> <xs:alternative test="@kind eq 'magazine'" type="MagazineType" /> <xs:alternative test="(@kind ne 'book') and (@kind ne 'magazine')" type="xs:error" /></xs:element>

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Open Content

The <openContent> and <defaultOpenContent> elements enable instance documents to contain extension elements interleaved among the elements declared by the schema.

Example: the Book element has open content:

<xs:element name="Book"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:gYear"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

In this instance document extension elements have been interleaved among the <Title>, <Author>, <Date>, <ISBN>, and <Publisher> elements:

<Book> <r:Binding>Hardcover</r:Binding> <Title>My Life and Times</Title> <r:Size>5 x 7</r:Size> <Author>Paul McCartney</Author> <r:InStock>true</r:InStock> <Date>1998</Date> <r:Category>Non-fiction</r:Category> <ISBN>1-56592-235-2</ISBN> <r:NumPages>299</r:NumPages> <Publisher>McMillin Publishing</Publisher> <r:AvailableOnTape>false</r:AvailableOnTape></Book>

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Schema-wide Attributes

defaultAttributes is used to specify a set of attributes that apply to every complexType in a schema document.

Example: The Book element has a required id attribute and an optional class attribute:

<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" defaultAttributes="myDefaultAttributes" elementFormDefault="qualified">

<xs:element name="Book"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:gYear"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element>

<xs:attributeGroup name="myDefaultAttributes"> <xs:attribute name="id" type="xs:ID" use="required" /> <xs:attribute name="class" type="xs:NMTOKENS" /> </xs:attributeGroup></xs:schema>

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Vendor Unique Extensions

XML Schema 1.1 vendors can add their own datatypes and facets.

Example: A vendor creates a new decimal datatype and a facet for specifying the delimiter to be used in the decimal value:

<xs:simpleType name="money"> <xs:restriction base="vendor:decimal"> <vendor:delimiter value="," /> <xs:restriction></xs:simpleType>

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Conditional Inclusion (a.k.a Version Control)

XML Schema 1.1 introduces a new namespace, the version control namespace. By convention vc: is used to prefix items in this namespace. vc:minVersion and vc:maxVersion may be placed as attributes on an element declaration to indicate which version of the schema specification the declaration was written to. vc:typeAvailable and vc:typeUnavailable may be placed as attributes on an element declaration to signal to a schema validator that a vendor-unique datatype is being used by the element. vc:facetAvailable and vc:facetUnavailable may be placed as attributes on an element declaration to signal to a schema validator that a vendor-unique facet is being used by the element.

Example: here are two declarations of an element Book; the first declaration is used by schema validators that implement the XML Schema 3.2 specification (or later); the second declaration is used by schema validators that implement any version between 1.1 and (excluding) 3.2:

<element name="Book" vc:minVersion="3.2"> declare the Book element</element><element name="Book: vc:minVersion="1.1" vc:maxVersion="3.2"> declare the Book element</element>

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Conditional Inclusion (a.k.a Version Control)

Example: here are two declarations of an element cost; the first declaration is used by schema validators that understand the datatype vendor:decimal; the second declaration is used by schema validators that don't understand vendor:decimal:

<element name="cost" vc:typeAvailable="vendor:decimal" type="vendor:decimal" /> <element name="cost" vc:typeUnavailable="vendor:decimal" type="decimal" />

Example: here are two declarations of an element population; the first declaration is used by schema validators that understand the facet vendor:delimiter; the second declaration is used by schema validators that don't understand vendor:delimiter:

<element name="population" vc:facetAvailable="vendor:delimiter"> <simpleType> <restriction base="integer"> <vendor:delimiter test="," /> </restriction> </simpleType></element><element name="population" vc:facetUnavailable="vendor:delimiter" type="integer" />

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Inherited Attributes

Attributes can be declared to be inheritable. Inheritable attributes can be used by descendant elements that contain <alternative> elements.

See example on next slide

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Example: the root element, BookStore, declares the attribute xml:lang as inheritable. The descendant Book element has two alternative elementsthat specify the content of Publisher based on the inherited xml:lang attribute:

<element name="BookStore"> <complexType> <sequence> <element name="Book" maxOccurs="unbounded"> <complexType> <sequence> … <xs:element name="Publisher" type="xs:string">

<xs:alternative test="@xml:lang eq 'en'"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="Wrox Press" /> <xs:enumeration value="'McMillan Publishing" /> </xs:restriction> </xs:simpleType> </xs:alternative> <xs:alternative test="@xml:lang eq 'fr'"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="'Bayard Presse" /> <xs:enumeration value="'Le Castor Astral" /> </xs:restriction> </xs:simpleType> </xs:alternative> </xs:element>

</sequence> </complexType> </element> </sequence> <attribute ref="xml:lang" inheritable="true" /> </complexType></element>

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Unordered Content using the <all> Element

The <all> element has been enhanced to allow elements with multiple occurrences. Also, <all> can have the wildcard, <any>, at any child position.

Example: the content of Book is: any number of extension elements, any number of Authors, Title, Date, ISBN, and Publisher, and they can be arranged in any order in instance documents:

<xs:element name="Book"> <xs:complexType> <xs:all> <xs:any maxOccurs="unbounded"/> <xs:element name="Author" maxOccurs="unbounded"/> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element>

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substitutionGroup can Substitute with Multiple Elements

The substitutionGroup capability has been enhanced so that an element can substitute with multiple elements.

Example: the <metro> element is substitutable for either <metrorail> or <subway>:

<xs:element name="metro" substitutionGroup="metrorail subway" type="xs:NCName" />

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New Attributes of the <any> and <anyAttribute> Wildcard Elements

The <any> and <anyAttribute> wildcard elements have been enhanced with additional attributes that allow you to indicate the kind of extension elements or attributes not allowed. The notNamespace attribute is used to indicate the namespace that extension elements or attributes cannot come from. The notQName attribute is used indicate an element or attribute that is not allowed.

Example: the first wildcard does not allow extension elements from the http://www.example.org namespace; the second wildcard does not allow extension attributes from the http://www.example.org namespace; the third wildcard does not allow xsl:value-of as an extension element:

<any notNamespace="http://www.example.org"/> <anyAttribute notNamespace="http://www.example.org"/> <any notQName="xsl:value-of"/>

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More Flexible Rules for Wildcards

Wildcards (<xs:any>) are important tools for extensible languages, but in XSD 1.0, it is difficult or impossible to use wildcards near optional content. XSD 1.1 is much more flexible.


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Example: in XSD 1.0 the element declaration shown here is not legal, because there are documents with elements like <NumPages> that could match either the explicit element declaration or the wildcard. In XSD 1.1, this schema is valid, and the <NumPages> element is validated as an integer by the element declaration; the <Reviews> and <Binding> elements are validated against the wildcard.

<xs:element name="Book"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string" minOccurs="0"/> <xs:element name="NumPages" type="xs:integer" minOccurs="0"/> <xs:any minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType></xs:element>----------<Book> <Title>The Origin of Wealth</Title> <NumPages>321</NumPages> <Reviews>Excellent</Reviews> <Binding>Hardcover</Binding></Book>

More Flexible Rules for Wildcards

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Enhanced Usage of the ID Datatype

In XML Schema 1.1 an element can have multiple attributes of type ID and the ID type can have a fixed or default value.

Example: the <Stereo> element has two ID attributes, model-number and serial-number; the Food attribute has a fixed ID value:

<element name="Stereo"> <complexType> <sequence> … </sequence> <attribute name="model-number" type="ID" use="required" /> <attribute name="serial-number" type="ID" use="required" /> </complexType></element>

<attribute name="Food" type="ID" fixed="Popcorn" />

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The <override> Element

The <override> element replaces the XML Schema 1.0 <redefine> element, which has been deprecated. The <override> element is used to replace the contents of a globally declared item in another schema.


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The <override> Element

Example: Office-calendar.xsd declares a <meeting> element with content <start-time>, <end-time>, and <room-number>. Conference-calendar.xsd overrides <meeting>'s content with <track-id>, <speaker>, and <room-capacity>:

Office-calendar.xsd declares a meeting element:

<xs:element name="meeting"> <xs:complexType> <xs:sequence> <xs:element name="start-time" type="xs:time" /> <xs:element name="end-time" type="xs:time" /> <xs:element name="room-number" type="xs:string" /> </xs:sequence> </xs:complexType></xs:element>

Conference-calendar.xsd overrides the meeting element:

<xs:override schemaLocation="office-calendar.xsd"> <xs:element name="meeting"> <xs:complexType> <xs:sequence> <xs:element name="track-id" type="xs:string" /> <xs:element name="speaker" type="xs:string" /> <xs:element name="room-capacity" type="xs:nonNegativeInteger" /> </xs:sequence> </xs:complexType> </xs:element></xs:override>

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targetNamespace on Element and Attribute Declarations

An XSD 1.0 Schema Document with one targetNamespace could not restrict a type using locally-declared elements from another targetNamespace. In XML Schema 1.1 you can do this by adding a targetNamespace attribute to each such "foreign" element and attribute in the restriction.


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targetNamespace on Element and Attribute Declarations

Example: this complexType restricts books:Book, which is in another namespace; targetNamespace is placed on each element declaration:

<xs:schema targetNamespace="http://www.libraries.org" xmlns:books="http://www.books.org">

<xs:import namespace="http://www.books.org" schemaLocation="Books.xsd"/>

<xs:complexType name="BookInLibrary"> <xs:complexContent> <xs:restriction base="books:Book"> <xs:sequence> <xs:element name="Title" type="xs:string" targetNamespace="http://www.books.org"/> <xs:element name="Author" type="xs:string" maxOccurs="2" targetNamespace="http://www.books.org"/> <xs:element name="Date" type="xs:gYear" targetNamespace="http://www.books.org"/> <xs:element name="ISBN" type="xs:string" targetNamespace="http://www.books.org"/> <xs:element name="Publisher" type="xs:string" targetNamespace="http://www.books.org"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> </xs:schema>

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The anyAtomicType Datatype

The anyAtomicType is the union of the value spaces of all the primitive types.

Example: this illustrates the anyAtomicType datatype:

<element name="Value" type="anyAtomicType" />---<Value xsi:type="xs:string">Hello World</Value><Value xsi:type="xs:decimal">12.36</Value><Value xsi:type="xs:boolean">true</Value>

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The dateTimeStamp Datatype

A dateTimeStamp value is identical to the dateTime datatype, except it requires time zone be specified.

Example: this illustrates the dateTimeStamp datatype:

<element name="birthdate" type="dateTimeStamp" />---<birthdate>1976-06-21T16:04:00-6:00</birthdate><birthdate>1980-01-01T24:00:00-6:00</birthdate>

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The yearMonthDuration Datatype

A yearMonthDuration value is a constrained version of the duration datatype; only years and months are specified.

Example: this illustrates the yearMonthDuration datatype:

<element name="eventDuration" type="yearMonthDuration" />---<eventDuration>P1Y3M</eventDuration><eventDuration>P15M</eventDuration>

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The dayTimeDuration Datatype

A dayTimeDuration value is a constrained version of the duration datatype; only day and time are specified.

Example: this illustrates the dayTimeDuration datatype:

<element name="conferenceDuration" type="dayTimeDuration" />---<conferenceDuration>P35DT01H22M30S</conferenceDuration><conferenceDuration>PT11H</conferenceDuration>

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New Facets

Here are the new facets:– assertion: use this to constrain a simpleType– explicitTimezone: use this with date datatypes to

specify whether the time zone is required

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Let's Dive In!

• That's the 5 minute introduction.

• As you see, there's lots of powerful new capabilities in XML Schema 1.1

• Let's examine each of them in depth.

• Happy learning!

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Expressing assertions using the <assert> element

http://www.w3.org/TR/xmlschema11-1/#cAssertions

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Example 1

Create a schema for this XML instance document:

<Document classification="secret"> <Para classification="unclassified"> ... </Para> <Para classification="secret"> ... </Para> <Para classification="unclassified"> ... </Para> <Para classification="secret"> ... </Para></Document>

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Things the Schema Should Check


Are the correct elements and attributes being used? Are the classification values correct?

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Are the correct elements and attributes being used? Are the classification values correct?

Grammar checks

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One more thing to check


Ensure that no <Para> element has a classification higher than the <Document> element's classification

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top-secret is higher than secret is higher than confidential is higher than unclassified

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Ensure that no <Para> element has a classification higher than the <Document> element's classification

Business rule check

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XML Schema 1.0

XML Schema 1.0 just supported grammar checking. For the classification rule we needed to use Schematron. We typically created a validation pipeline:


XML SchemaValidator

SchematronValidator

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New Capability!

XML Schema 1.1 supports both grammar checking and business rule checking.

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The <assert> element

• The XML Schema 1.1 <assert> element is used to make assertions about the values of elements and attributes.

• I will use it to assert:If the Document's classification is secret then no Paras have a value equal to top-secret.If the Document's classification is confidential then no Paras have a value equal to top-secret and no Paras have a value equal to secret.If the Document's classification is unclassified then no Paras have a value equal to top-secret and no Paras have a value equal to secret and no Paras have a value equal to confidential.

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Use XPath 2.0 to Express Assertions

<assert test="xpath" />

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Use XPath 2.0 to Express Assertions

<assert test="xpath" />

The XPath must evaluate to either true or false. If it evaluates to true then the data (in the instance document) is valid, otherwise the data is invalid.

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Here's the Assertion

<xs:assert test="if (@classification eq 'secret') then not(Para/@classification = 'top-secret') else if (@classification eq 'confidential') then not(Para/@classification = 'top-secret') and not(Para/@classification = 'secret') else if (@classification eq 'unclassified') then not(Para/@classification = 'top-secret') and not(Para/@classification = 'secret') and not(Para/@classification = 'confidential') else true()" />

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Equivalent<xs:assert test="if (@classification eq 'secret') then not(Para/@classification = 'top-secret') else if (@classification eq 'confidential') then not(Para/@classification = 'top-secret') and not(Para/@classification = 'secret') else if (@classification eq 'unclassified') then not(Para/@classification = 'top-secret') and not(Para/@classification = 'secret') and not(Para/@classification = 'confidential') else true()" />

<xs:assert test="if (@classification eq 'secret') then not(Para/@classification = ('top-secret')) else true() "/><xs:assert test="if (@classification eq 'confidential') then not(Para/@classification = ('top-secret', 'secret')) else true() "/><xs:assert test="if (@classification eq 'unclassified') then not(Para/@classification = ('top-secret', 'secret', 'confidential')) else true()" />

3 asserts:

1 assert:

Much easier to understand, I think

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Asserts are and’ed

• If you have multiple assert elements, then they are and’ed together.

• Thus, for a value to be valid, all asserts must evaluate to true.

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Here's where Assertions go

Place assertions at the bottom of a <complexType> element:

<xs:element name="Document"> <xs:complexType> <xs:sequence> <xs:element name="Para" type="ParaType" maxOccurs="unbounded"> </xs:element> </xs:sequence> <xs:attribute name="classification" type="classificationLevels" use="required"/> <xs:assert test="if (@classification eq 'secret') then else … true()" /> </xs:complexType></xs:element>

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ElementDocument

ElementPara

ElementPara

ElementPara

TextOne if …

TextAnd I …

TextReady to

Attributeclassification=“secret”

Attributeclassification=“unclassified”

Attributeclassification=“confidential”

Attributeclassification=“unclassified”

Assert: if (@classification eq 'secret') then … else … true()

Assertions always look down

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Assertions always look down

• Note that I placed the assertion on the <Document> element, not the <Para> element.

• From the <Document> element my XPath expression "looked down" to the <Para> (child) elements.

• If I had placed the assertion on the <Para> element my XPath expression would need to "look up" to the <Document> element (parent). In fact, that won't do what I want. The <para> is the root for the XPath evaluation, so the XPath won't even see the <Document> element.

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When evaluating an assertion, the element containing the assertion is considered to be the root element.

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When evaluating an assertion, the element containing the assertion is considered to be the root element.

Now you understand why assertions always "look down"

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The validity of an element depends only on the content of that element, and not on the context where it is used.

Michael Kay

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Position of Assertions

Place the assertions on the complexType of the root element

This will give you flexibility in what you incorporate into your assertion: at a later date you may decide to incorporate additional factors into your assertion; since you've positioned it at the top of the XML tree you will be able to use any data in the current document.

When you want to optimize something like business rules for a particular document type, or for a major subsection of a document, then putting the assertions on the type of the document root or the root element of the subtree makes sense.

Two use cases to illustrate the positioning of assertions:

Place the assertions on the type that the assertion applies to.

This makes the type – and its assertions – reusable across documents.

The best way to ensure rules are followed is to get them right in front of people at the exact point where the guidance is relevant. [Ross]

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ElementBarnesAndNoble

ElementBook

Text

assert: string-length(. le 140)

ElementTitle

ElementAuthor

ElementDate

ElementISBN

ElementPublisher

Text Text Text Text

assert: string-length(.//Publisher le 140)

Position of assert is a Crucial Difference

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Crucial Difference

<BarnesAndNoble> assert: string-length(.//Publisher le 140) <Book> … <Publisher>____</Publisher> assert: string-length(. le 140) </Book> …</BarnesAndNoble>

Note that both assertions are stating that the length of the Publisher element must be less than 140 characters. However, the assertions are critically different. The assertion on BarnesAndNoble says that the BarnesAndNoble element is invalid if the Publisher has a string length greater than 140 characters, whereas the assertion on Publisher says that the Publisher element is invalid if it has a string length greater than 140 characters. Do you see the difference? It’s important that you do.

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Run it!

xml-schemas1.1examples

assertionsclassification

classification.xmlclassification.xsd

Here's my folder hierarchy:

Validate the instance document against the schema

Do Lab1

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Equivalent

<xs:element name="BarnesAndNoble"> <xs:complexType> <xs:sequence> <xs:element ref="Book" maxOccurs="unbounded" /> </xs:sequence> <xs:assert test=“every $i in Book satisfies string-length($i/Publisher) le 140" /> </xs:complexType> </xs:element>

<xs:element name="BarnesAndNoble"> <xs:complexType> <xs:sequence> <xs:element ref="Book" maxOccurs="unbounded" /> </xs:sequence> <xs:assert test="not(Book[string-length(Publisher) gt 140])" /> </xs:complexType> </xs:element>

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Does this work?

<xs:element name="BarnesAndNoble"> <xs:complexType> <xs:sequence> <xs:element ref="Book" maxOccurs="unbounded" /> </xs:sequence> <xs:assert test="Book[string-length(Publisher) le 140]" /> </xs:complexType> </xs:element>

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No!

<xs:element name="BarnesAndNoble"> <xs:complexType> <xs:sequence> <xs:element ref="Book" maxOccurs="unbounded" /> </xs:sequence> <xs:assert test="Book[string-length(Publisher) le 140]" /> </xs:complexType> </xs:element>

Read the assertion as: “I assert that there exists a Book such that the string-length of its Publisher is le 140.”

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Example 2Consider this element declaration:

<xs:element name="Publisher" type="xs:string"/>

What values can the <Publisher> element have in an XML instance document:

<Publisher>_________</Publisher>

Suppose the Publisher element is being used by Book:

<xs:element name="Book"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string"/> <xs:element name="Date" type="xs:gYear"/> <xs:element name="ISBN" type="xs:string"/> <xs:element ref="Publisher" /> </xs:sequence> </xs:complexType> </xs:element>

Okay, what values can Publisher have?

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Copyright © [2012]. Roger L. Costello. All Rights Reserved. Did you answer:

The value of Publisher can be any unconstrained string.

If you're using XML Schema 1.1 then your answer may be wrong.

The <assert> element can impose additional constraints on the Publisher element. For example, the <Book> element is nested within a <BarnesAndNoble> element, which has an <assert> element that constrains the Publisher element to a maximum string length of 140 characters:


The <Book> element is also nested within a <Borders> element, which has an <assert> element that constrains the Publisher element to either 'McMillin Publishing', 'Dell Publishing Co.', 'Harper & Row', or 'Wrox Press':

<xs:element name="Borders"> <xs:complexType> <xs:sequence> <xs:element ref="Book" maxOccurs="unbounded" /> </xs:sequence> <xs:assert test="not(Book[not(Publisher = ('McMillin Publishing', 'Dell Publishing Co.','Harper & Row', 'Wrox Press'))])" /> </xs:complexType> </xs:element>

See the examples folder, assertions, whats-the-value-space

70


What values can Publisher have?

- It could be an unbounded string, or

- It could be a string of max length 140, or

- It could be an enumeration list, 'McMillin Publishing', 'Dell Publishing Co.', 'Harper & Row', or 'Wrox Press'

- Or, it could be something else.

That's interesting, but

so what?

continued

71


Q: What are the valid values of Publisher?

A: You can't tell just by looking at the declaration.

72


To understand an element you must understand its ancestors.(Ancestors may exert an action at a distance.)

Do Lab2

73


Example 3

• countries.xml is a list of countries.

• My schema declares a <country> element. I want to validate that its value matches one of the values in countries.xml

<countries>

<country>Afghanistan</country> <country>Albania</country> <country>Algeria</country> <country>American Samoa</country> <country>Andorra</country> <country>Angola</country> <country>Anguilla</country> <country>Antarctica</country> <country>Antigua and Barbuda</country> <country>Argentina</country> <country>Armenia</country> …</countries>

countries.xml

<Example>

<country>______</country> </Example>

Check that this value matches a value in here

74


<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<element name="Example"> <complexType> <sequence> <element name="country" type="string" /> </sequence> <assert test="country = doc('countries.xml')//country" /> </complexType> </element>

</schema>

See the folder: validating-against-an-external-document

75


Bad News

• The cross-document validation described in the previous two slides is not permitted!

• You cannot use the doc() function in an assertion.

76


Why?

I think the working group felt that introducing context-dependent validation (where the validity of a document depends on factors other than the schema and the instance document) was a risky architectural innovation, and possibly a step that would be later regretted.

Michael Kay

77


Example 4

• In this example I write an assertion which asserts that a meeting's end time must be greater than its start time.

• I have three versions of the schema:– No namespace: the schema doesn't use

targetNamespace– One namespace: the schema has a

targetNamespace– Two namespaces: the start-time is in one

namespace, the end-time is in another

78


ElementExample

Elementmeeting

Elementstart-time

Elementend-time

Text Text

assert: end-time gt start-time

79


V1 – No Namespace<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<element name="Example"> <complexType> <sequence> <element name="meeting-time"> <complexType> <sequence> <element name="start-time" type="time" /> <element name="end-time" type="time" /> </sequence> <assert test="end-time gt start-time" /> </complexType> </element> </sequence> </complexType> </element>

</schema>

See meeting-time_v1.xsd in the folder: meeting-time

80


v2 – One Namespace<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.meeting.org" elementFormDefault="qualified">

<element name="Example"> <complexType> <sequence> <element name="meeting-time"> <complexType> <sequence> <element name="start-time" type="time" /> <element name="end-time" type="time" /> </sequence> <assert test="end-time gt start-time" xpathDefaultNamespace="##targetNamespace" /> </complexType> </element> </sequence> </complexType> </element>

</schema> See meeting-time_v2.xsd in the folder: meeting-time

81


xpathDefaultNamespace

• It is an optional attribute of xs:assert• Here are its legal values:

– ##targetNamespace: this means the default namespace within the XPath expression is the targetNamespace

– ##defaultNamespace: this means the default namespace within the XPath expression is the schema's default namespace (which may be different than the targetNamespace)

– ##local: this means the default namespace within the XPath expression is no namespace (this is the default value)

– http://www.example.org: this means the default namespace within the XPath expression is the http://www.example.org namespace

82


Equivalent!

<assert test="end-time gt start-time" xpathDefaultNamespace="##targetNamespace" />

xmlns:m="http://www.meeting.org"…<assert test="m:end-time gt m:start-time" />

83


Place xpathDefaultNamespace on <xs:schema> element

• Rather than placing xpathDefaultNamespace on each <xs:assert> element, you can place it on the <xs:schema> element.

• Thus, in one fell-swoop you can provide a default namespace for all xpath expressions.

<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.meeting.org" xpathDefaultNamespace="##targetNamespace" elementFormDefault="qualified">

. . .</schema> Do Lab3

84


v3 – Two Namespaces<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.meeting.org" xmlns:t="http://www.times.org" elementFormDefault="qualified">

<import namespace="http://www.times.org" schemaLocation="times.xsd" />

<element name="Example"> <complexType> <sequence> <element name="meeting-time"> <complexType> <sequence> <element name="start-time" type="time" /> <element ref="t:end-time" /> </sequence> <assert test="t:end-time gt start-time" xpathDefaultNamespace="##targetNamespace" /> </complexType> </element> </sequence> </complexType> </element>

</schema>

See meeting-time_v3.xsd in the folder: meeting-time

85


times.xsd

targetNamespace=“http://www.times.org”

end-time

meeting-time.xsd

targetNamespace=“http://www.meeting.org”

Examplemeetingstart-time

“import”

Do Lab4

86


ElementExample

Elementcouples

Elementname

Elementname

Text Text

assert: ??? (What is a useful business rule?)

. . .

87


ElementExample

Elementcouples

Elementname

Elementname

Text Text

assert: count(name) mod 2 = 0

. . .

88


Example 5

• All the XPath functions are available for use in your assertion. (http://www.w3.org/TR/xpath-functions/)

• Here I use the count() function to assert that the number of <name> elements in <couples> must be even:

<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<element name="Example"> <complexType> <sequence> <element name="couples"> <complexType> <sequence> <element name="name" maxOccurs="unbounded" /> </sequence> <assert test="count(name) mod 2 = 0" /> </complexType> </element> </sequence> </complexType> </element>

</schema> See couples.xsd in the folder: couples

Do Lab5

89


Example 6

• In XSD 1.0 it was difficult to express "If the value of <A> is xyz then there should be child element <foo> and if the value of <A> is rst then there should be a child element <bar>"

• That is, expressing conditional presence was difficult.

• It is easy in XSD 1.1, using assertions

90


Conditional Presence

<Transportation> <mode>air</mode> <*****>_____</*****> </Transportation>

The element here depends on the value here

91


Conditional Presence

<xs:element name="Transportation"> <xs:complexType> <xs:sequence> <xs:element name="mode" type="modeType" /> <xs:choice> <xs:element name="airplane" type="xs:string" /> <xs:element name="boat" type="xs:string" /> <xs:element name="car" type="xs:string" /> </xs:choice> </xs:sequence> <xs:assert test="if (mode eq 'air') then child::airplane else if (mode eq 'water') then child::boat else if (mode eq 'ground') then child::car else false()" /> </xs:complexType></xs:element>

See conditional-mode-of-transportation.xsd in the folder: conditional-presence

Do Lab6

92


Conflicting <assert> elements(Who wins?)

<BarnesAndNoble> assert: string-length(.//Publisher ge 140) <Book> … <Publisher>____</Publisher> assert: string-length(. le 70) </Book> …</BarnesAndNoble>

93


Suppose one <assert> element says "The value of <Publisher> must be a string not to exceed 140 characters in length."

Another <assert> element says "The value of <Publisher> must be a string not to exceed 70 characters in length."

Which <assert> element wins?

Example: I have an <assert> element on the root element (<BarnesAndNoble>) which says "The value of each <Publisher> element must be a string not to exceed 140 characters in length." I have another <assert> element directly on the <Publisher> element which says: "The value of <Publisher> must be a string not to exceed 70 characters in length." Is <Publisher> constrained to a length of 140 characters or 70 characters?

Conflicting <assert> elements(Who wins?)

94

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<xs:element name="Publisher"> <xs:complexType> <xs:simpleContent> <xs:extension base="xs:string"> <xs:assert test="not(string-length(.) gt 70)" /> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element>

<xs:element name="Book"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string"/> <xs:element name="Date" type="xs:gYear"/> <xs:element name="ISBN" type="xs:string"/> <xs:element ref="Publisher" /> </xs:sequence> </xs:complexType> </xs:element>


</xs:schema>

<Publisher>'s value must be less than 70 characters in length.

<Publisher>'s value must be less than 140 characters in length.

See BookStore_v2.xsd in the folder: whats-the-value-space

95


Answer

The assertions are "anded" together: the value must satisfy all of them. Inthis case it means the value must be no longer than 70.

It's quite possible to have assertions that really conflict, e.gtest="string-length() > 100" and test="string-length() < 3". In that casethere are no valid instances. Indeed, it's possible to have a singleassertion that can never be satisfied, e.g. "string-length() < 0" or moresimply, test="false()"

Michael Kay

96


Example 7

A paragraph cannot appear nested within another paragraph unless there is an intervening table.

Use <assert> to express this rule:

<Example> <paragraph> <table>…</table> <paragraph> <table>…</table> <paragraph> <table>…</table> <paragraph> … </paragraph> </paragraph> </paragraph> </paragraph>

</Example>

paragraph is recursive.

97


<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<xs:element name="Example"> <xs:complexType> <xs:sequence> <xs:element name="paragraph" type="paragraphType" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> </xs:element>

<xs:complexType name="paragraphType" mixed="true"> <xs:sequence> <xs:element name="table" type="xs:string" minOccurs="0" /> <xs:element name="paragraph" type="paragraphType" minOccurs="0" /> </xs:sequence> <xs:assert test="if (paragraph) then paragraph/preceding-sibling::table else true()" /> </xs:complexType>

</xs:schema>

See paragraph.xsd in the paragraph folder

98


Relocate the <assert>

• In the previous example the <assert> was located right where it is needed.

• Question: What XPath expression would you use if the <assert> was positioned on the root element?

99


not(.//paragraph[child::*[1][self::paragraph]])

Answer

100


Quiz

• The paraType is defined recursively. Thus, there is no limit to the nesting.

• Write an <assert> which limits the nesting to no more than 10 deep.

101


ElementLevel_1_Manager_Signoffs

Elementpurchase-request

Elementitem

Elementcost

Text Text

assert: every $i in purchase-request satisfies $i/cost le 10000assert: not(purchase-request[cost gt 10000])

A Level 1 manager has a maximum signature authority of $10K.

Elementpurchase-request

Elementitem

Elementcost

Text Text

. . .

Equivalent:

102


Example 8Use <assert> to implement this rule:

A Level 1 manager has a maximum signature authority of $10K.

<element name="Level_1_Manager_Signoffs"> <complexType> <sequence> <element name="purchase-request" maxOccurs="unbounded"> <complexType> <sequence> <element name="item" type="string" /> <element name="cost" type="decimal" /> </sequence> </complexType> </element> </sequence> <assert test="not(purchase-request[number(cost) gt 10000])"/> </complexType> </element>

Here's the schema:

See Level_1_Manager_Signoffs.xsd in the purchase-requests folder

103


Subtype inherits assert’s from base type

• Suppose complexType A is a subtype of complexType B (i.e., A derives-by-extension from B or A derives-by-restriction from B).

• If B has one or more <xs:assert> elements, then A inherits those assert’s.

104


Publication

TitleAuthorDateassert: Date gt 1970

BookPublication

ISBNPublisherassert: Publisher eq ‘Wrox Press’

"extends"

BookPublication has two assert’s

105


<xsd:complexType name="Publication"> <xsd:sequence> <xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Date" type="xsd:date"/> </xsd:sequence> <xsd:assert test="Date gt xsd:date('1970-01-01')" xpathDefaultNamespace="##targetNamespace" /></xsd:complexType>

<xsd:complexType name="BookPublication"> <xsd:complexContent> <xsd:extension base="Publication"> <xsd:sequence> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> <xsd:assert test="Publisher = 'Wrox Press'" xpathDefaultNamespace="##targetNamespace" /> </xsd:extension> </xsd:complexContent></xsd:complexType>

"extends"

See BookStore.xsd in the inherit-asserts-from-base-complexType folder

106


Recap

• XML Schema 1.1 now enables you to make assertions, using the <assert> element:

<assert test="XPath" />• The <assert> element is placed at the bottom

of a <complexType>.• The XPath cannot use the doc() function to

reference other documents.• The XPath cannot "look up" the XML tree to

the parent, grandparent, cousins, etc

107


The portion of the DTD for XML Schema 1.1 that pertains to <assert>

<!ELEMENT assert ((annotation)?)><!ATTLIST assert test CDATA #REQUIRED  id ID #IMPLIED xpathDefaultNamespace CDATA #IMPLIED>

<!ELEMENT complexType ((annotation)?, (simpleContent | complexContent | openContent?, (all | choice | sequence | group)?), ((attribute | attributeGroup)*, (anyAttribute)?), assert*)>

<!ELEMENT extension ((annotation)?, (openContent?, (all | choice | sequence | group)?)) , ((attribute | attributeGroup)*, (anyAttribute)?), assert*)>

<!ELEMENT restriction ((annotation)?, (simpleType?, (minExclusive | minInclusive | …)?)) , ((attribute | attributeGroup)*, (anyAttribute)?), assert*)>

108


Schematron Niche?

• XML Schema 1.0 did not have the ability to make assertions; thus, expressing things such as co-constraints was not possible.

• Schematron filled that niche.• Q: Now that XML Schema 1.1 has the ability to make

assertions, where does Schematron stand?• A: Recall that you cannot do cross document

validation using the <assert> element. Schematron can. This is an important niche that Schematron can fill.

See my tutorial on Schematron: http://www.xfront.com/schematron/

109


Example to illustrate the need for Cross Document Validation

<countries>

<country>Afghanistan</country> <country>Albania</country> <country>Algeria</country> <country>American Samoa</country> <country>Andorra</country> <country>Angola</country> <country>Anguilla</country> <country>Antarctica</country> <country>Antigua and Barbuda</country> <country>Argentina</country> <country>Armenia</country> …</countries>

countries.xml

<Example>

<country>______</country> </Example>

Check that this value matches a value in here

110

Copyright © [2012]. Roger L. Costello. All Rights Reserved. Another example to illustrate the

need for Cross Document Validation

ATM

<Request type="withdrawal"> <Amount>$500</Amount> <Member>John Doe</Member> <TimeStamp>2009-07-27T08:08:00</TimeStamp></Request>

<BankAccount> <Member>John Doe</Member> <Balance>$1000</Balance></BankAccount>

Check that this value is less than this value.

111


Constraining simpleTypes using the assertion facet

http://www.w3.org/TR/xmlschema11-2/#rf-assertions

112


Example 1

Create a schema for this XML instance document:

<Example>

<even-integer>____</even-integer> </Example>

Even integers only, e.g. 2, 4, 6, 8, 10, …

113


The assertion Facet

XML Schema 1.1 has a new facet: assertion

<element name="even-integer"> <simpleType> <restriction base="integer"> <assertion test="xpath" /> </restriction> </simpleType></element>

114


The assertion Facet

XML Schema 1.1 has a new facet: assertion

<element name="even-integer"> <simpleType> <restriction base="integer"> <assertion test="xpath" /> </restriction> </simpleType></element>

Notice that "test" is a departure from the other facets, which use "value", e.g.<minInclusive value="100" />

115


The $value Variable

• This is a built-in variable.

• It's value is the value of the current (context) element/attribute.<element name="even-integer"> <simpleType> <restriction base="integer"> <assertion test="$value mod 2 = 0" /> </restriction> </simpleType></element>

I assert that the value of <even-integer> must satisfy this XPath expression, i.e. only even integers are valid

116


Run it!

xml-schemas1.1examples

assertionsclassificationeven-integers

even-integers.xmleven-integers_v1.xsd

Here's my folder hierarchy:

Validate the instance document against the schema

117


assertion Facet: it's for Every Data Type

• The <assertion> facet can be used with every data type.

• Multiple <assertion> facets can be used.– These facets may repeat:

• pattern

• enumeration

• assertion

– Unlike the pattern and enumeration facets, if there are multiple assertion facets then they are “and-ed” together.

118


assertion plus other facets

You can use other facets along with assertion:<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<element name="Example"> <complexType> <sequence> <element name="even-integer"> <simpleType> <restriction base="integer"> <minInclusive value="0" /> <maxInclusive value="100" /> <assertion test="$value mod 2 = 0" /> </restriction> </simpleType> </element> </sequence> </complexType> </element>

</schema>

The integer must be even and it must be between 0 and 100

See even-integers_v2.xsd

Do Lab7

119


assertion plus matches() can replace the pattern facet

<xs:simpleType name="English-language-family-name"> <xs:restriction base="xs:string"> <xs:minLength value="2" /> <xs:maxLength value="100" /> <xs:pattern value="[a-zA-Z' \.-]+" /> </xs:restriction></xs:simpleType>

Instead of this:

<xs:simpleType name="English-language-family-name"> <xs:restriction base="xs:string"> <xs:minLength value="2" /> <xs:maxLength value="100" /> <xs:assertion test="matches($value, ‘^[a-zA-Z' \.-]+')$" /> </xs:restriction></xs:simpleType>

Do this:

120

Copyright © [2012]. Roger L. Costello. All Rights Reserved. There's a tricky point in substituting XPath regexs in assertion facet for XSD regexs in pattern facet. XPath regex language *adds* the ^ and $ meta-characters, which force a match at the beginning and end of the string, respectively. These aren't needed in XSD regexes, since all matches are *always* done against the complete string. So these two facets mean different things: <xs:pattern value="[\sa-zA-Z0-9,;:\.]*"/> <xs:assertion test="matches($value, '[\sa-zA-Z0-9,;:\.]*')"/> The regex is exactly the same in these two patterns, but *are not equivalent*. The pattern facet matches the regex against *the entire value* of the simple type; in contrast, the matches function in the assertion facet matches the regex against *any part of the value* of the simple type. Note, for example, that in neither case is the hyphen (-) allowed in the regular expression. A simple type with the first facet above would fail if the value contains a hyphen. However, a simple type with the second facet above would NOT fail with a hyphen; alternatively, the second facet would pass as long as *any* part of the value matches the regex. To have equivalent facets, you would need to add the ^ and $ meta-characters to the XPath regex, as follows: <xs:pattern value="[\sa-zA-Z0-9,;:\.]*"/> <xs:assertion test="matches($value, '^[\sa-zA-Z0-9,;:\.]*$')"/> The pattern facet is the same as above and repeated simply for ease in comparison. The only difference in the assertion is that the ^ begins the regex, and $ ends the regex; these meta-characters force the regex to match the entire string. These two facets are equivalent. Another major difference: XPath regex supports back references. Example taken from the spec: The regular expression ('|").*\1 matches a sequence of characters delimited either by an apostrophe at the start and end, or by a quotation mark at the start and end. This makes XPath regexs much more vulnerable to Regular Expression Denial of Service (ReDOS) attacks, since the *only* way to implement back references is with a backtracking algorithm. At least a smart XSD validating parser could choose an efficient regex engine not vulnerable to ReDOS, but there's no such option with XPath.

Jonathan Cranford

121


Conditional Type Alternatives(a.k.a. CTA)

http://www.w3.org/TR/xmlschema11-1/#cTypeAlternative

122


Example 1

<Publication kind="_________">

</Publication>

If it's magazine then the content mustbe MagazineType. If kind="book" then the content must be BookType.

123


Type Dependence

The type of <Publication> depends on the value of this


</Publication>

124


xs:alternative

• The <alternative> element is used to provide alternate types for an element.

• Which type is selected is based on the results of a test.

<alternative test="XPath'" type="type" />

125



If this evaluates to true, then this type must be used.

126


<xs:element name="Publication" type="PublicationType"> <xs:alternative test="@kind eq 'magazine'" type="MagazineType" /> <xs:alternative test="@kind eq 'book'" type="BookType" /></xs:element>

The declared type for <Publication>


</Publication>

which type?Instance document:

Schema document:

127



The alternative types for <Publication>

128



"If the value of the kind attribute is 'magazine' then use MagazineType as <Publication>'s type."

129



"If the value of the kind attribute is 'book' then use BookType as <Publication>'s type."

130



"If the value of the kind attribute is not 'book' and not 'magazine' then use PublicationType as <Publication>'s type."

Do Lab8

See publication_v1.xsd in the folder: type-alternatives/publication

131


Alternates must derive from

The type specified in <alternative> must derive from the element's declared type

PublicationType

BookType MagazineType

In order for BookType and MagazineType to be alternative types, they must derive from <Publication>'s type (PublicationType)

132


PublicationType

TitleAuthor (0 - unbounded occurrences)Date

BookType

ISBNPublisher

"extends"

MagazineType

TitleDate

"restrict"


Publication

Attribute: kind

133


<xs:complexType name="PublicationType"> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:gYear"/> </xs:sequence> <xs:attribute name="kind" type="xs:string" /></xs:complexType>

Since the kind attribute is of type string, the value of @kind can be 'book' (<alternative> will then force BookType as the type), or @kind can be 'magazine' (<alternative> will then force MagazineType as the type), or @kind can be anything else and then PublicationType will be the type. Q: Suppose you always want the type to be restricted to one of the types specified by the <alternative> elements; how would you do that?

134


A: Restrict the value of @kind <xs:complexType name="PublicationType"> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:gYear"/> </xs:sequence> <xs:attribute name="kind"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="magazine" /> <xs:enumeration value="book" /> </xs:restriction> </xs:simpleType> </xs:attribute></xs:complexType>

Now there's only two possible values for @kind, and the <alternative> elements specify the type for each value.


Do Lab9

135


Inlined Type

On the <alternative> element you can specify the name of a type, or you can define a type inline:


<alternative test="XPath'"> <complexType> … </complexType></alternative>

<alternative test="XPath'"> <simpleType> … </simpleType></alternative>

136

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <xs:element name="Publication" type="PublicationType" maxOccurs="unbounded"> <xs:alternative test="@kind eq 'magazine'"> <xs:complexType> <xs:complexContent> <xs:restriction base="PublicationType"> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:gDate"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> </xs:alternative> <xs:alternative test="@kind eq 'book'"> <xs:complexType> <xs:complexContent> <xs:extension base="PublicationType"> <xs:sequence> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> </xs:alternative></xs:element>

inlinedtypedefinitions


137


xpathDefaultNamespace

The <assert> element, the <assertion> facet, and the <alternative> element have an optional attribute, xpathDefaultNamespace:

<alternative test="XPath'" type="type" xpathDefaultNamespace="___" />

<assert test="xpath" xpathDefaultNamespace="___" />

The values for ___ are: ##targetNamespace, ##defaultNamespace, ##local, anyURI

<assertion test="xpath" xpathDefaultNamespace="___" />

138


Can't look up, can't look down

• The XPath expression in the <alternative> element can only reference attributes of the current (context) element.

• It cannot reference ancestor elements.

• It cannot reference descendent elements.

139


Can't look up, can't look down

<xs:element name="Publication" type="PublicationType"> <xs:alternative test="___'" type="…" /></xs:element>

This XPath expression can only reference attributes of Publication.

140


Can use <assert> instead

• Rather than using <alternative> you could use <assert>

• Here's how:– Group all the elements together. Make some of

them optional. • ISBN and Publisher should occur only with

@kind='book' so make them optional.

– Create an assertion that identifies the child elements that should be present, given the value of @kind

141


Group all elements together

<xs:complexType name="PublicationType"> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:gYear"/> <xs:element name="ISBN" type="xs:string" minOccurs="0"/> <xs:element name="Publisher" type="xs:string" minOccurs="0"/> </xs:sequence> <xs:attribute name="kind" type="xs:string" /> <xs:assert test="…" /> </xs:complexType>

142


<xs:assert test="if (@kind eq 'book') then Title and Date and ISBN and Publisher and empty(* except (Title[1], Date[1], Author, ISBN[1], Publisher[1])) else if (@kind eq 'magazine') then Title and Date and empty(* except (Title[1], Date[1])) else Title and Date and empty(* except (Title[1], Date[1], Author))" />

Create an assertion

143


<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

<xs:element name="Example"> <xs:complexType> <xs:sequence> <xs:element name="Publication" type="PublicationType" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> </xs:element>

<xs:complexType name="PublicationType"> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:gYear"/> <xs:element name="ISBN" type="xs:string" minOccurs="0"/> <xs:element name="Publisher" type="xs:string" minOccurs="0"/> </xs:sequence> <xs:attribute name="kind" type="xs:string" /> <xs:assert test="if (@kind eq 'book') then Title and Date and ISBN and Publisher and empty(* except (Title[1],Date[1],Author,ISBN[1],Publisher[1])) else if (@kind eq 'magazine') then Title and Date and empty(* except (Title[1],Date[1])) else Title and Date and empty(* except (Title[1],Date[1], Author))" /> </xs:complexType>

</xs:schema>


Do Lab10

144


Consider this book publication:

<Publication kind="book"> <Title>Everything is Miscellaneous</Title> <Author>David Weinberger</Author> <Date>2007</Date> <ISBN>0-8050-8811-3</ISBN> <Publisher>Henry Holt and Company, LLC</Publisher> </Publication>

Next, consider this magazine publication:

<Publication kind="magazine"> <Title>Science News</Title> <Date>2005</Date> </Publication>

Notice the *kind* attribute in both examples.

If its value is 'book' then the content of <Publication> is:

- Title - Author - Date - ISBN - Publisher

And if its value is 'magazine' then the content of <Publication> is:

- Title - Date

Subject: Best Practice: constrain an element's content by (1) a run-time selection of alternate types or (2) a run-time selection of child elements using an XPath expression?

145

Copyright © [2012]. Roger L. Costello. All Rights Reserved. PROBLEM STATEMENT

What is best practice for constraining the content of Publication?

XML SCHEMA 1.1 PROVIDES TWO APPROACHES

XML Schema 1.1 provides two approaches to constraining the content of the <Publication> element.

APPROACH #1: ALTERNATE TYPES

Create a BookType and a MagazineType and then select one of them to be <Publication>'s type depending on @kind:

if @kind = 'book' then select BookType else select MagazineType

Here's how it is expressed in XML Schema 1.1:

<xs:element name="Publication" type="PublicationType"> <xs:alternative test="@kind eq 'magazine'" type="MagazineType" /> <xs:alternative test="@kind eq 'book'" type="BookType" /> </xs:element>

You see the (new) <alternative> element being used to select a type for <Publication> based on the value of @kind.

146


APPROACH #2: XPATH EXPRESSION

Let the content of <Publication> be a collection of all the elements (both book elements and magazine elements) and set them optional:

- Title (0,1) - Author (0, unbounded) - Date (0,1) - ISBN (0,1) - Publisher (0,1)

Then create an XPath expression that selects the set of children for <Publication> depending on the value of @kind:

if (@kind eq 'book') then Title and Date and ISBN and Publisher and empty(* except (Title[1],Date[1],Author,ISBN[1],Publisher[1])) else if (@kind eq 'magazine') then Title and Date and empty(* except (Title[1],Date[1])) else true()

147


Here's how it is expressed in XML Schema 1.1:

<xs:element name="Publication"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string" minOccurs="0"/> <xs:element name="Author" type="xs:string" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:gYear" minOccurs="0"/> <xs:element name="ISBN" type="xs:string" minOccurs="0"/> <xs:element name="Publisher" type="xs:string" minOccurs="0"/> </xs:sequence> <xs:attribute name="kind" type="xs:string" /> <xs:assert test="if (@kind eq 'book') then Title and Date and ISBN and Publisher and empty(* except (Title[1],Date[1],Author,ISBN[1],Publisher[1])) else if (@kind eq 'magazine') then Title and Date and empty(* except (Title[1],Date[1])) else Title and Date and empty(* except (Title[1],Date[1], Author))" /> </xs:complexType></xs:element>

148


You see that the content of <Publication> is all the book and magazine elements and they are optional.

You see an XPath expression within the (new) <assert> element being used to constrain which child elements are allowed within Publication based on the value of @kind.

TWO APPROACHES

You have seen two ways of solving the problem of constraining the content of <Publication>:

(a) Run-time selection of alternate types

(b) Run-time selection of child elements using XPath

DEFINITION OF "RUN-TIME"

By "run-time" I mean that the content of <Publication> is not determined until an instance document is validated against a schema.

WHICH IS BEST PRACTICE?

Which approach is best practice?

What are the pros and cons of each approach?

149


I think the best advice is probably: if you can do it conveniently using Conditional Type Alternative (CTA), i.e., the <alternative> element,(as you can here), then do. Otherwise use assertions.

There are a number of reasons for this.

(1) What is sometimes called the "rule of least power": don't use a chainsaw to snap a twig.

(2) More concretely:

(2a) A schema validator is more likely to adopt a streaming implementation for CTA than for assertions

(2b) The schema validator is likely to produce better diagnostics if youdescribe the constraint using CTA

(2c) You are likely to get a more precise type annotation on the element if you use CTA, which gives benefits when writing schema-aware stylesheets and queries.

Michael Kay

150


An advantage of using <assert> rather than <alternative> is that you can factor in more information using <assert>. The <assert> can be placed at the top of the document, thereby enabling it to factor in information from the entire document. With <alternative> you can make a decision based only on the attributes of the current element. That's pretty limiting

Roger Costello

151


Example 2

<Meeting start-time="_____" end-time="______">

</Meeting>

1. Check that the end-time is greater than the start-time. use the <assert> element

2. If the end-time is before noon, bring tea to the meeting, if the end-time is after noon, bring juice to the meeting. use the <alternative> element

152


MeetingType

MorningMeeting

Tea

"extends"

AfternoonMeeting

Juice

"extends"

Subject

153


Sample Instance Document

<?xml version="1.0" encoding="utf-8"?><Example>

<Meeting start-time="08:00:00" end-time="09:00:00"> <Subject>Discuss the new project</Subject> <Tea>green</Tea> </Meeting>

<Meeting start-time="13:00:00" end-time="14:00:00"> <Subject>Discuss the new project</Subject> <Juice>apple</Juice> </Meeting> </Example>

154





Use <assert> to check that this value is after the value of start-time

155





This must be of type MorningMeeting since end-time is before noon. Express this type constraint using <alternative>

156


<xs:element name="Example"> <xs:complexType> <xs:sequence> <xs:element name="Meeting" type="MeetingType" maxOccurs="unbounded"> <xs:alternative test="@end-time le '12:00:00'" type="MorningMeeting" /> <xs:alternative test="@end-time gt '12:00:00'" type="AfternoonMeeting" /> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

<xs:complexType name="MeetingType"> <xs:sequence> <xs:element name="Subject" type="xs:string"/> </xs:sequence> <xs:attribute name="start-time" type="xs:time" /> <xs:attribute name="end-time" type="xs:time" /> <xs:assert test="@end-time gt @start-time" /> </xs:complexType>

<xs:complexType name="MorningMeeting"> <xs:complexContent> <xs:extension base="MeetingType"> <xs:sequence> <xs:element name="Tea" type="xs:string"/> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType>

<xs:complexType name="AfternoonMeeting"> <xs:complexContent> <xs:extension base="MeetingType"> <xs:sequence> <xs:element name="Juice" type="xs:string"/> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType>

</xs:schema>

See meeting.xsd in the folder: type-alternatives/meeting

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Example 3

<Beverage current-time="_____"> </Beverage>

If the current-time is before noon, the value of <Beverage> must be "tea". If the current-time is after noon, the value of <Beverage> must be "juice"

158


BeverageType

MorningBeverage

Datatype xs:stringrestricted to one value: "tea"

"restrict"

AfternoonBeverage

"restrict"

Datatype: xs:stringAttribute: current-time

Datatype xs:stringrestricted to one value: "juice"

159


Sample Instance Document


<Beverage current-time="08:00:00">tea</Beverage>

<Beverage current-time="13:00:00">juice</Beverage> </Example>

160



<Beverage current-time="08:00:00">tea</Beverage>

<Beverage current-time="13:00:00">juice</Beverage> </Example>

This must be of type MorningBeverage since current-time is before noon. Express this type constraint using <alternative>

161


<xs:element name="Example"> <xs:complexType> <xs:sequence> <xs:element name="Beverage" type="BeverageType" maxOccurs="unbounded"> <xs:alternative test="@current-time le '12:00:00'" type="MorningBeverage" /> <xs:alternative test="@current-time gt '12:00:00'" type="AfternoonBeverage" /> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

<xs:complexType name="BeverageType"> <xs:simpleContent> <xs:extension base="xs:string"> <xs:attribute name="current-time" type="xs:time" use="required" /> </xs:extension> </xs:simpleContent> </xs:complexType>

<xs:complexType name="MorningBeverage"> <xs:simpleContent> <xs:restriction base="BeverageType"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="tea" /> </xs:restriction> </xs:simpleType> </xs:restriction> </xs:simpleContent> </xs:complexType>

<xs:complexType name="AfternoonBeverage"> … </xs:complexType>

</xs:schema>

See beverage.xsd in the folder: type-alternatives/beverage

162


Multiple <alternative> elements apply ... which one wins?

Suppose that several <alternative> elements apply. Which one will be used?

Example: the below <Beverage> element has two <alternative> elements. If the value of the current-time attribute is 08:00:00 then both <alternative> elements apply. Which one will be used?

<xs:element name="Beverage" type="BeverageType"> <xs:alternative test="@current-time le '12:00:00'" type="MorningBeverage" /> <xs:alternative test="@current-time le '09:00:00'" type="EarlyMorningBeverage" /></xs:element>

163


Answer

The first alternative with a test that evaluates to true is used.

Given a Type Table T and an element information item E, T conditionally selects a type S for E in the following way. The {test} expressions in T's {alternatives} are evaluated, in order, until one of the Type Alternatives ·successfully selects· a type definition for E, or until all have been tried without success.

Section 3.3.4.1 (http://www.w3.org/TR/xmlschema11-1/#sec-sistd):

164


The Portion of the DTD for XML Schema 1.1

that Pertains to <alternative>

<!ELEMENT alternative ((annotation)?, (simpleType | complexType)?) ><!ATTLIST alternative test CDATA #REQUIRED  type CDATA #IMPLIED  xpathDefaultNamespace CDATA #IMPLIED id ID #IMPLIED >

<!ELEMENT element ((annotation)?, (complexType | simpleType)?, (alternative)*, (unique | key | keyref)*)>

165


xs:error

http://www.w3.org/TR/xmlschema11-1/#xsd-error

166


xs:error Datatype

• This is a new datatype

• It is used to trigger an error

• (Recall the example in the previous section) We can use xs:error to generate an error if @kind is neither 'book' or 'magazine'

<xs:element name="Publication" type="PublicationType" maxOccurs="unbounded"> <xs:alternative test="@kind eq 'magazine'" type="MagazineType" /> <xs:alternative test="@kind eq 'book'" type="BookType" /> <xs:alternative test="(@kind ne 'book') and (@kind ne 'magazine')" type="xs:error" /></xs:element>

If @kind is neither 'book' or 'magazine' then generate an error

Do Lab11

167


Equivalent!

If the kind attribute is declared like this:

<attribute name="kind"> <simpleType> <restriction base="string"> <enumeration value="book" /> <enumeration value="magazine" /> </restriction> </simpleType></attribute>

Then the following CTA will ensure that <Publication> has MagazineType content when kind equals 'magazine' and <Publication> has BookType when kind equals 'book' and an error is generated when kind has some other value:


If the kind attribute is declared like this:

<attribute name="kind" type="string" />

Then this CTA has the same functionality as the other one:

<xs:element name="Publication" type="PublicationType"> <xs:alternative test="@kind eq 'magazine'" type="MagazineType" /> <xs:alternative test="@kind eq 'book'" type="BookType" /> <xs:alternative test="(@kind ne 'book') and (@kind ne 'magazine')" type="xs:error" /></xs:element>

In this case xs:error is used to trigger an error when kind does not have the value 'magazine' or 'book'.

168


xs:error redundant?

• The previous slide shows that xs:error is not needed – the same functionality can be achieved without it.

• Q: Is xs:error redundant?

• A: No. Suppose PublicationType is declared in a schema that you cannot modify. And suppose it declares kind to be of type string. Then you will have to use xs:error.

169


Example 2

Suppose there is a Book schema that you want to use. It declares an optional Review element:

<xs:element name="Book"> <xs:complexType> <xs:sequence> <xs:element ref="Title" /> <xs:element ref="Author" /> <xs:element ref="Date" /> <xs:element ref="ISBN" /> <xs:element ref="Publisher" /> <xs:element ref="Review" minOccurs="0" /> </xs:sequence> </xs:complexType></xs:element>

<xs:element name="Title" type="xs:string"/><xs:element name="Author" type="xs:string"/><xs:element name="Date" type="xs:gYear"/><xs:element name="ISBN" type="xs:string"/><xs:element name="Publisher" type="xs:string"/><xs:element name="Review" type="xs:string"/>

170


Example 2 (cont.)

Suppose that in your schema you don't want the Review element, so you override Review's type (we'll see the <override> element later):

<xs:override schemaLocation="Book.xsd"> <xs:element name="Review" type="xs:error" /></xs:override>

<xs:element name="BookStore"> <xs:complexType> <xs:sequence> <xs:element ref="Book" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType></xs:element>

"Review is optional, but if you do use it you'll get an error."

See the error folder for this example. Thanks to Michael Sperberg-McQueen for this example.

171



172


Motivation

<Meeting start-time="_____" end-time="_____"> <Beverage>_____</Beverage></Meeting>

Use the MorningBeverage type if end-time is before noon. Use the AfternoonBeverage type if end-time is after noon.

173


Q: Will this Work?

<alternative test="../@end-time le 12:00:00" type="MorningBeverage" /><alternative test="../@end-time ge 12:00:00" type="AfternoonBeverage" />

174


A: No!

<alternative test="../@end-time le 12:00:00" type="MorningBeverage" /><alternative test="../@end-time le 12:00:00" type="AfternoonBeverage" />

Trying to reference an ancestor (parent). The <alternative> element can only reference attributes on the current element.

175


If only ….

ElementMeeting

ElementBeverage

Attributesstart-timeend-time

If only we could get these attributes to be "inherited" by the Beverage element …

176


If an attribute of an ancestor element of E is declared as inheritable, then you can refer to it in an <alternative> element as if it appeared on element E itself.

<attribute name="start-time" type="time" inheritable="true" /><attribute name="end-time" type="time" inheritable="true" />

We can!

177


<xs:element name="Example"> <xs:complexType> <xs:sequence> <xs:element name="Meeting" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="Beverage" type="BeverageType"> <xs:alternative test="@end-time le '12:00:00'" type="MorningBeverage" /> <xs:alternative test="@end-time gt '12:00:00'" type="AfternoonBeverage" /> </xs:element> </xs:sequence> <xs:attribute name="start-time" type="xs:time" inheritable="true" /> <xs:attribute name="end-time" type="xs:time" inheritable="true" /> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType></xs:element>

The <alternative> elements are testing end-time, which is an attribute of Meeting. Normally that's illegal. Since end-time is declared to be inheritable, it is as though it was declared by the Beverage element. And thus the <alternative> element can use it.

See meeting-beverage.xsd in the folder: inheritable-attributes/meeting-beverage

178


Only <alternative>

• Inherited attributes can be used by only the <alternative> element, not the <assert> element.

• Inherited attributes provide a mechanism to circumvent the “can only look at attributes” restriction.

• Since inherited attributes can only be used by <alternative> elements, the <alternative> element should be favored.

179


Which Design is Better?

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>New Riders</Publisher> </Book></BookStore>

<?xml version="1.0"?><BarnesAndNoble> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>New Riders</Publisher> </Book></BarnesAndNoble>

- or -

180


Business Rule

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>New Riders</Publisher> </Book></BookStore>

<?xml version="1.0"?><BarnesAndNoble> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>New Riders</Publisher> </Book></BarnesAndNoble>

Business RuleThe value of Publisher depends on the store:• If the store is BarnesAndNoble then Publisher can be either Wrox Press or New Riders• If the store is Borders then Publisher can

be either Norton Press or friendsofed

181


Invalid

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>O’Reilly</Publisher> </Book></BookStore>

<?xml version="1.0"?><BarnesAndNoble> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>O’Reilly</Publisher> </Book></BarnesAndNoble>

Given the business rule on the previous slide, this data is invalid.

182


What is Invalid?

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>O’Reilly</Publisher> </Book></BookStore>


Is BarnesAndNoble invalid or is Publisher invalid?

Is BookStore invalid or is Publisher invalid?

183


What is the Business Rule a Statement About?

• Is the business rule a statement about what are valid BarnesAndNoble and Borders documents?

• Or, is the business rule a statement about what is a valid value of Publisher given its context?

184


B.R. is a Statement re:B&N and Borders

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> Assert: Book/Publisher = (‘Wrox Press’, ‘New Riders’) <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>O’Reilly</Publisher> </Book></BookStore>

<?xml version="1.0"?><BarnesAndNoble> Assert: Book/Publisher = (‘Wrox Press’, ‘New Riders’) <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>O’Reilly</Publisher> </Book></BarnesAndNoble>

Design the XML Schema with the business rule expressed on the root element:

See Assert-Version.xsd in the folder: inheritable-attributes/book

185


B.R. is a Statement re:Publisher

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>O’Reilly</Publisher> Alternative: if @storename=‘BarnesAndNoble’ then text() = (‘Wrox Press’, ‘New Riders’) Alternative: if @storename=‘Borders’ then text() = (‘Norton Press’, ‘friendsofed’) </Book></BookStore>


Design the XML Schema with the business rule expressed on the Publisher element:

See Alternative-Version.xsd in the folder: inheritable-attributes/book

The business rule, applied to the Publisher element, cannot be expressed given this design!

186

Copyright © [2012]. Roger L. Costello. All Rights Reserved. How you interpret your business rules has a profound impact on XML design

Consider this book store document:

<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>New Riders</Publisher> </Book> ...</BookStore>

The document is used by a community that has this business rule:

-------------------------------------------------Business Rule

The value of Publisher depends on the store:

If the store is BarnesAndNoble then Publisher can be either Wrox Press or New Riders

If the store is Borders then Publisher can be either Norton Press or friendsofed------------------------------------------------- Given that business rule, this is invalid (because 'friendsofed' is an invalid publisher for the store 'BarnesAndNoble'):

187


<?xml version="1.0"?><BookStore storename="BarnesAndNoble"> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>friendsofed</Publisher> </Book></BookStore>

What is invalid? - Is BookStore invalid? - Or, is Publisher invalid? Is the business rule a statement about what are valid BookStores? Or, is the business rule a statement about what are valid values of Publisher given its context? The question is important. It's answer has a profound impact on XML design. IMPACT ON XML DESIGN If the business rule is a statement about what are valid BookStores then, when you design your XML Schema, you should position an <assert> element on the BookStore element declaration: Assert: Book/Publisher = ('Wrox Press', 'New Riders')

188


If the business rule is a statement about what are valid values of Publisher given its context then, when you design your XML Schema, you should position <alternative> elements in the Publisher element declaration: Alternative: if @storename='BarnesAndNoble' then text() = ('Wrox Press', 'New Riders') Alternative: if @storename='Borders' then text() = ('Norton Press', 'friendsofed') and you should declare the storename attribute to be "inheritable".

You must specify the store name in an attribute value and not in an element name. The following XML design would make it impossible to implement the business rule: <?xml version="1.0"?><BarnesAndNoble> <Book> <Title>Don't Make Me Think</Title> <Author>Steve Krug</Author> <Date>2006</Date> <ISBN>0-321-34475-8</ISBN> <Publisher>New Riders</Publisher> </Book></BarnesAndNoble> QUESTION Is the business rule a statement about what are valid BookStores or is it a statement about what are valid values of Publisher given its context?

189


Popular inherited attribute

<Root xml:lang="fr"> … any element in here can have an <alternative> element that uses xml:lang …</Root>

declare this to be inheritable

Do Lab12

190

Copyright © [2012]. Roger L. Costello. All Rights Reserved. We've seen that by declaring an attribute to be inheritable, descendant elements can use the attribute in their <alternative> elements.

But suppose an attribute is declared to be both inheritable and required (use="required"). Does that mean descendant elements must display that attribute in instance documents?

For example, <Meeting> has two required, inheritable attributes:

<element name="Meeting"> <complexType> <sequence> <element name="Beverage" type="b:BeverageType"> <alternative test="@end-time le '12:00:00'" type="b:MorningBeverage" /> <alternative test="@end-time gt '12:00:00'" type="b:AfternoonBeverage" /> </xs:element> </sequence> <attribute name="start-time" type="xs:time" use="required" inheritable="true" /> <attribute name="end-time" type="xs:time" use="required" inheritable="true" /> </complexType></element>

Q: In an instance document must the <Beverage> element have the two inherited attributes:

<Meeting start-time="___" end-time="___">

<Beverage start-time="___" end-time="___"> ... </Beverage>

</Meeting>

191


A: No. Inheritable attributes do not appear in instance documents.

192


Multiple inheritable attributes with the same name ... who wins?

Suppose a <Beverage> element has multiple ancestor elements with an inheritable attribute, start-time. The <Beverage> element has an <alternative> element that references start-time. Which start-time applies?

Example: Suppose each start-time attribute is inheritable:

--------------------------------------<Conference start-time="08:00:00">

<Meeting start-time="13:00:00"> <Beverage>Juice</Beverage>

</Meeting>

</Conference>--------------------------------------

Which start-time is visible to Beverage?

193


AnswerIt's the closest one

The rules are in 3.3.5.6 Inherited Attributes. To paraphrase, this says that:

(a) all inheritable attributes of ancestors of an element E are "potentiallyinherited" by E

(b) the actual [inherited attributes] are attributes that are potentiallyinherited excluding any that are "masked" by an inner inherited attribute ofthe same name.

Section 3.12.4 (rule 1.1.3) then says that in practice, the only [inheritedattributes] that are relevant are those that do not have the same name asone of the element's "real" attributes.

One corner case to be aware of is

<a att="3"> <b att="4"> <c/> </b></a>

where element <a> defines @att as an inherited attribute, while element <b>defines @att as a non-inherited attribute. In this case element <c> effectivelyhas the value <c att="3"/>.

Michael Kay

194


Inherited Attribute + <alternative> + <assert>

• Imagine an <alternative> element that uses inherited attributes. And an element in the type specified by the <alternative> applies a constraint on a descendent element.

• Thus, to understand that descendent element requires understanding its ancestor element that contains the <assert>. But the <assert> depends on the <alternative> which uses an inherited attribute.

• Phew! Things can get pretty complicated.

195


Schema-wide Attributes (defaultAttributes)

http://www.w3.org/TR/xmlschema11-1/#declare-schema

196


Motivation

• Sometimes you want every complexType to have an attribute, such as an ID attribute or a class attribute.

• In XML Schema 1.0 you had to declare those attributes on every complexType.

• Now you can state on the <schema> element, "Hey, all complexTypes shall have the attributes that I've declared in this ____ attributeGroup."

197



<xs:element name="BookStore"> <xs:complexType> <xs:sequence> <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

<xs:attributeGroup name="myDefaultAttributes"> <xs:attribute name="id" type="xs:ID" use="required" /> <xs:attribute name="class" type="xs:NMTOKENS" /> </xs:attributeGroup>

</xs:schema>

The attributes declared in the attributeGroup named "myDefaultAttributes" are to be applied to each complexType

198


ElementBookStore

ElementBook

Text

These elements have @id and @class

ElementTitle

ElementAuthor

ElementDate

ElementISBN

ElementPublisher

Text Text Text Text

The non-leaf elements get the attributes.

199


<?xml version="1.0"?><BookStore xmlns="http://www.books.org" id="Barnes-and-Noble"> <Book id="McCartney"> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> </Book> <Book id="Bach"> <Title>Illusions</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book id="Krishnamurti"> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book></BookStore>

BookStore and each Book is required to have an id attribute, and optionally a class attribute

See the defaultAttributes folder, within it the bookStore folder, and BookStore.xsd

200


Scope of defaultAttributes

defaultAttributes: class

defaultAttributes: id

Book.xsd

BookStore.xsd

"import"

This default attribute only applies to the complexTypes within this schema file

This default attribute only applies to the complexTypes within this schema file

201


The defaultAttributes applies only to types definedin the schema document for which the defaultAttributesattribute is specified. Types defined in other schemadocuments are not affected, whether they are included oracquired via import or by some other means.

Michael Sperberg-McQueen

202


<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.bookstore.org" xmlns="http://www.bookstore.org" xmlns:bk="http://www.book.org" defaultAttributes="bookstoreDefaultAttributes" elementFormDefault="qualified">

<xs:import namespace="http://www.book.org" schemaLocation="Book.xsd" />

<xs:element name="BookStore"> <xs:complexType> <xs:sequence> <xs:element ref="bk:Book" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> </xs:element>

<xs:attributeGroup name="bookstoreDefaultAttributes"> <xs:attribute name="id" type="xs:ID" use="required" /> </xs:attributeGroup>

</xs:schema>

BookStore.xsd

<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.book.org" xmlns="http://www.book.org" defaultAttributes="bookDefaultAttributes" elementFormDefault="qualified">

<xs:element name="Book"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element>

<xs:attributeGroup name="bookDefaultAttributes"> <xs:attribute name="class" type="xs:NMTOKENS" use="optional" /> </xs:attributeGroup>

</xs:schema>

Book.xsd

Only @class applies here

Only @id applies here

203


<?xml version="1.0"?><BookStore id="Borders" xmlns="http://www.bookstore.org" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.books.org BookStore.xsd"> <Book class="McCartney" xmlns="http://www.book.org"> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> </Book> <Book class="Bach" xmlns="http://www.book.org"> <Title>Illusions</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book class="Krishnamurti" xmlns="http://www.book.org"> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book></BookStore>

@id can only be used on BookStore

@class can only be used on Book

See the defaultAttributes folder, within it the bookStore folder, and BookStore_v2.xsd

Do Lab13

204


defaultAttributesApply

• Okay, you specify defaultAttributes and now every complexType has the attributes.

• But suppose a complexType doesn't want those attributes? How do you "turn off" defaultAttributes?

• Answer: on the complexType add this attribute: defaultAttributesApply="false"

• That says, "The default attributes don't apply to this complexType."

http://www.w3.org/TR/xmlschema11-1/#dcl.ctd.attuses

205



<xs:element name="BookStore"> <xs:complexType defaultAttributesApply="false"> <xs:sequence> <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

<xs:attributeGroup name="myDefaultAttributes"> <xs:attribute name="id" type="xs:ID" use="required" /> <xs:attribute name="class" type="xs:NMTOKENS" /> </xs:attributeGroup>

</xs:schema>

BookStore does not have the id or class attributes (but each Book does)

See the defaultAttributes folder, within it the bookStore folder, and BookStore_v3.xsd

206


The <all> element

http://www.w3.org/TR/xmlschema11-1/#all-mg

207


Almost the same as before

• Just as in XML Schema 1.0:– An <all> element must just contain elements. It cannot

contain <sequence> or <choice>– The <all> element cannot be embedded within a

<sequence> or <choice>– The <all> element is not repeatable, i.e. this is not allowed:

<all maxOccurs="unbounded">• There are three big changes in 1.1:

1. An <element> in <all> is not restricted to one occurrence2. The <any> element can be used in <all>3. The <all> can be used in a base type and then the base type

can be extended with a type that uses <all>

208


You couldn't do this in 1.0

<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:all> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element>

XML Schema 1.0 did not allow this.

209


<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:all> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element>

"The content of Book is one Title, any number of Authors, one Date, one ISBN, one Publisher, and they can occur in any order."

See BookStore_v1.xsd in the folder: all/book-store

You can do this in 1.1

210



<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:all> <xs:any/> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element>

XML Schema 1.0 did not allow this.

211


<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:all> <xs:any/> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" maxOccurs="unbounded"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element>

"The content of Book is one Title, any number of Authors, one Date, one ISBN, one Publisher, one element from any namespace, and they can occur in any order."



212

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:all> <xs:any minOccurs="0"/> <xs:element ref="Author" maxOccurs="unbounded"/> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element><xs:element name="Author" type="xs:string" />

<Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> <Author>John Ghostwriter</Author></Book>

How does a validator validate this? Against <any/> or the Author declaration?


213

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:any minOccurs="0"/> <xs:element ref="Author" maxOccurs="unbounded"/> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element><xs:element name="Author" type="xs:string" />

<Book> <Author>Paul McCartney</Author> <Author>John Ghostwriter</Author> <Title>My Life and Times</Title> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher></Book>

How does a validator validate this? Against <any/> or the Author declaration?


214


If an element could match either an element declaration or a wildcard, then the element declaration is chosen.

Rule:

215

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:all> <xs:any minOccurs="0"/> <xs:element ref="Author" maxOccurs="unbounded"/> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element><xs:element name="Author" type="xs:string" />

<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:any minOccurs="0"/> <xs:element ref="Author" maxOccurs="unbounded"/> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element><xs:element name="Author" type="xs:string" />

Non-deterministic content models.

216


Consider this:

<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:any minOccurs="0"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Title" type="xs:string"/> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

This will fail because when it gets to the first <Author> (in an instance document) it commits to the declaration for Author. So, when it gets to the second <Author> it expects Title.

Recommendation: when using <any> don't use <sequence>, always use <all>.

See book.xsd in the folder: all/book

217


XSD 1.1 allows certain classes of non-deterministic content models prohibited by XSD 1.0!

Do Lab14

218



<xs:complexType name="appliance"> <xs:all> <xs:element name="description" type="xs:string"/> <xs:element ref="warranty" minOccurs="0"/> </xs:all> </xs:complexType> <xs:complexType name="juiceAppliance"> <xs:complexContent> <xs:extension base="appliance"> <xs:all> <xs:element name="name" type="xs:string"/> <xs:element name="image" type="imageType"/> <xs:element name="weight" minOccurs="0" type="xs:positiveInteger" /> <xs:element name="cost" type="xs:decimal" maxOccurs="unbounded" /> <xs:element name="retailer" type="xs:anyURI"/> </xs:all> </xs:extension> </xs:complexContent> </xs:complexType>

XML Schema 1.0 did not allow you to extend a non-empty base type that uses <all>.

219


"The content of juiceAppliance is description, warranty, name, image, weight, cost, retailer and they can occur in any order."

See juicers.xsd in the folder: all/juicers


<xs:complexType name="appliance"> <xs:all> <xs:element name="description" type="xs:string"/> <xs:element ref="warranty" minOccurs="0"/> </xs:all> </xs:complexType> <xs:complexType name="juiceAppliance"> <xs:complexContent> <xs:extension base="appliance"> <xs:all> <xs:element name="name" type="xs:string"/> <xs:element name="image" type="imageType"/> <xs:element name="weight" minOccurs="0" type="xs:positiveInteger" /> <xs:element name="cost" type="xs:decimal" maxOccurs="unbounded" /> <xs:element name="retailer" type="xs:anyURI"/> </xs:all> </xs:extension> </xs:complexContent> </xs:complexType>

220



<all> description warranty</all>

<all> name image weight cost retailer</all>

"extend"

Note: you can extend an <all> with an <all>, but not with a <sequence> or a <choice>.

221


Wildcard Schema Components

(i.e. <any> and <anyAttribute>)

http://www.w3.org/TR/xmlschema11-1/#Wildcards

222


<any namespace="_____________" />

This enables you to specify what elements you want, e.g. I want any element from the targetNamespace (##targetNamespace). But in XSD 1.0 there is no way to specify what you don't want: "I want any element, provided it doesn't come from the targetNamespace."

XML Schema 1.0

223


<any notNamespace="_____________" />

This enables you to specify what elements you don't want, e.g. I don't want any element from the targetNamespace (##targetNamespace). Or, I don't want any element from this namespace: http://www.example.org. Or, I don't want any element from no namespace.

New in XML Schema 1.1

224


Specifying what extension elements you don't want

<any notNamespace="##targetNamespace"/> allows the instance document to contain a new element, provided the element does not come from the

targetNamespace.

<any notNamespace="http://www.example.org"/> allows the instance document to contain a new element, provided the element does not come from this namespace: http://example.org

<any notNamespace="##local"/> allows the instance document to contain a new element, provided the element does not come from no namespace

Note: the value of notNamespace can be a list of ##targetNamespace, anyURIs, and ##local

See BookStore_v1.xsd in the folder: wildcards/book-store

225


<anyAttribute namespace="_____________" />

This enables you to specify what attributes you want, e.g. I want any attribute from the targetNamespace (##targetNamespace). But in XSD 1.0 there is no way to specify what you don't want: "I want any attribute, provided it doesn't come from the targetNamespace."

XML Schema 1.0

226


This enables you to specify what attributes you don't want, e.g. I don't want any attribute from the targetNamespace (##targetNamespace). Or, I don't want any attribute from this namespace: http://www.example.org. Or, I don't want any attribute from no namespace.

<anyAttribute notNamespace="_____________" />


227


Specifying what extension attributes you don't want

<anyAttribute notNamespace="##targetNamespace"/> allows the instance document to contain new attributes, provided the attributes do not come from the targetNamespace.

<anyAttribute notNamespace="http://www.example.org"/> allows the instance document to contain new attributes, provided the attributes do not come from this namespace: http://example.org

<anyAttribute notNamespace="##local"/> allows the instance document to contain new attributes, provided the attributes do not come from no namespace

Note: the value of notNamespace can be a list of ##targetNamespace, anyURIs, and ##local

228


<any notQName="_____________" />

This enables you to specify specific elements you don't want, e.g. I don't want the {http://www.example.org}numPages element.


229


Specifying what extension elements you don't want

<any notQName="xsl:value-of"/> allows the instance document to contain a new element, provided the element is not the <value-of> element from the xsl namespace

<any notQName="##defined"/> allows the instance document to contain a new element, provided its name is not the same as that of a global element declaration in the schema

<any notQName="##definedSibling"/> allows the instance document to contain a new element, provided its name is not the same as that of a sibling element

Note: the value of notQName can be a list of QNames, ##defined, and ##definedSibling

See BookStore_v2.xsd in the folder: wildcards/book-store

230


Open Content

http://www.w3.org/TR/xmlschema11-1/#Complex_Type_Definition_details

231


Definition of Open Content

<Book> <ISBN>0-06-064831-7</ISBN> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <Publisher>Harper & Row</Publisher></Book>

Design a schema so that any element, from any namespace, can occur at any of these places. Doing so makes the content of <Book> open. That is, <Book> has open content.

232


<xs:element name="Book"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

Dictionary definition of interleave: to insert pages between the pages of a book.

Read as: "Any elements, from any namespace, can be interleaved with the elements declared in the subsequent <sequence> content model."

Here's How To Do It

233


<?xml version="1.0"?><BookStore xmlns="http://www.books.org" xmlns:r="http://www.bookrepository.org" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.books.org BookStore.xsd http://www.bookrepository.org BookRepository.xsd"> <Book> <r:Binding>Hardcover</r:Binding> <Title>My Life and Times</Title> <r:Size>5 x 7</r:Size> <Author>Paul McCartney</Author> <r:InStock>true</r:InStock> <Date>1998</Date> <r:Category>Non-fiction</r:Category> <ISBN>1-56592-235-2</ISBN> <r:NumPages>299</r:NumPages> <Publisher>McMillin Publishing</Publisher> <r:AvailableOnTape>false</r:AvailableOnTape> </Book> <Book> <Publisher>Dell Publishing Co.</Publisher> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Title>Illusions The Adventures of a Reluctant Messiah</Title> </Book> <Book> <ISBN>0-06-064831-7</ISBN> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <Publisher>Harper & Row</Publisher> </Book></BookStore>

These new (extension) elements have been inserted (interleaved) with the elements declared in <sequence>

Example Instance Document That Validates Against the Schema

See BookStore_v1.xsd in the folder: open-content/book-store

234


Equivalent

<xs:element name="Book"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

<xs:element name="Book" type="BookType" />

<xs:complexType name="BookType"> <xs:openContent mode="interleave"> <xs:any /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence></xs:complexType>

The content of BookType is open. Book is of type BookType. Thus, the content of Book is open.

Book has a type which is open. Thus, the content of Book is open.

235


Any elements, any where, any number

If you declare <Book>'s content to have open content, then in the instance document you can insert extension elements around any child element within <Book>. And, you can insert any number of elements.

236


minOccurs, maxOccurs are ignored

<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any minOccurs="0" maxOccurs="unbounded" /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

minOccurs and maxOccurs are ignored. {0, unbounded} is the fixed setting. In other words, you can insert any number of elements before and after Title, Author, Date, ISBN, and Publisher.

237

Copyright © [2012]. Roger L. Costello. All Rights Reserved. It's okay to use @namespace,

@notNamespace, and @notQNameon the <any> element

<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any namespace="##other" /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

This specifies that the extension elements must come from a namespace other than the schema's targetNamespace.

238


Validate the Inserted Elements?

You can use the processContents attribute with the <any> element to control whether or not the inserted elements must be validated:

<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any processContents="lax" /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

"Hey schema processor, validate the inserted elements if you can. If you can't, then just skip them."

239



This will validate, even if there's no schema to validate the inserted elements.

240


<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any processContents="strict" /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>


"Hey schema validator, you must validate the inserted elements. If you can't validate them, then throw an error."

This will not validate if there's no schema to validate the inserted elements.

Do Lab15

241


<openContent> applies only to the children, not the grandchildren

Consider this <Book> element, declared to have open content:

<element name="Book"> <complexType> <openContent mode="interleave"> <any /> </openContent> <sequence> <element name="Title" type="string"/> <element name="Author"> <complexType> <sequence> <element name="FirstName" type="string"/> <element name="LastName" type="string"/> </sequence> </complexType> </element> <element name="Date" type="string"/> <element name="ISBN" type="string"/> <element name="Publisher" type="string"/> </sequence> </complexType></element>

Notice that the <Author> element has child elements, which are grandchildren of <Book>.

Extension elements can only be inserted before and after the *children* of Book. Extension elements cannot be inserted around the *grandchildren* of Book. Thus, extension elements cannot be inserted before or after <FirstName> and <LastName>.

242


The mode Attribute

• There are three possible values for mode:– interleave– suffix– none

• mode="interleave" means extension elements can be inserted anywhere. This is the default, i.e. if you omit the mode attribute then it defaults to mode="interleave"

• mode="suffix" means extension elements can only be inserted at the bottom (e.g. after the <Publication> element)

• mode="none" means that you can't insert new elements, i.e. it's not open content.

Q: Why bother with <openContent> and then specify mode="none"?

A: Suppose your complexType derives from someone else's complexType which has been defined to have open content.

Suppose you don't want open content; so, you can use mode="none" to turn off the open content.

<openContent mode="interleave"> <any /></openContent>

243


<xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:openContent mode="suffix"> <xs:any /> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

Any elements (from any namespace) can be inserted at the bottom of <Book> (after the <Publisher> element).

244


<Book> <ISBN>0-06-064831-7</ISBN> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <Publisher>Harper & Row</Publisher></Book> Can only put extension

elements here.

245


<Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> <r:Binding>Hardcover</r:Binding> <r:Size>5 x 7</r:Size> <r:InStock>true</r:InStock> <r:Category>Non-fiction</r:Category> <r:NumPages>299</r:NumPages> <r:AvailableOnTape>false</r:AvailableOnTape></Book>

The extension elements can only be inserted at the bottom of <Book>'s content model.


Do Lab16

246


Schema-wide Open Content

• You can specify at the top of the schema: "The entire schema is open"

• This is accomplished using the <xs:defaultOpenContent> element

<xs:defaultOpenContent mode="interleave"> <xs:any /></xs:defaultOpenContent>

Read as: "New elements, from any namespace, can be inserted before and after every element in the entire document."

247

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified">

<xs:defaultOpenContent mode="interleave"> <xs:any /> </xs:defaultOpenContent>

<xs:element name="BookStore"> <xs:complexType> <xs:sequence> <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

</xs:schema>

This must be at the top of the schema, following<xs:include>, <xs:import>, <xs:redefine>, and <xs:override>


248

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <?xml version="1.0"?><BookStore xmlns="http://www.books.org" xmlns:r="http://www.bookrepository.org" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.books.org BookStore.xsd http://www.bookrepository.org BookRepository.xsd">

<r:StoreName>Books R Us</r:StoreName> <Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> <r:Binding>Hardcover</r:Binding> </Book> <Book> <r:Size>5 x 7</r:Size> <Title>Illusions The Adventures of a Reluctant Messiah</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <r:NumPages>299</r:NumPages> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book></BookStore>

Observe the extension elements that have been inserted between the <Book> elements and within them.

Example XML instance document that conforms to the schema on the previous slide

249

Copyright © [2012]. Roger L. Costello. All Rights Reserved. Consider this schema, which uses <xs:defaultOpenContent> to make the entire schema open:

<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified">

<xs:defaultOpenContent mode="interleave"> <xs:any /> </xs:defaultOpenContent>

<xs:element name="BookStore"> <xs:complexType> <xs:sequence> <xs:element name="Book" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

</xs:schema>

Q: Can extension elements be added before and after the root element (BookStore)?

250


Q: Will this instance document validate against the schema on the previous slide? Note that the schema's root element has been wrapped within an extension element.

<?xml version="1.0"?><r:MyFavoriteBookStore xmlns:r="http://www.bookrepository.org"> <BookStore xmlns="http://www.books.org"> <Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> <r:Binding>Hardcover</r:Binding> </Book> <Book> <r:Size>5 x 7</r:Size> <Title>Illusions The Adventures of a Reluctant Messiah</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <r:NumPages>299</r:NumPages> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book> </BookStore></r:MyFavoriteBookStore>

251


A: No, extension elements cannot be inserted before or after the root element. The reason for this is that openness applies to types (i.e. complexTypes have open content); thus, only the content of the root element (BookStore), and its descendant elements are open.

Do Lab17

252


mode="none"

<xs:defaultOpenContent mode="______"> <xs:any /></xs:defaultOpenContent>

interleave or suffix

When specifying a schema-wide setting for open content, you cannot use mode="none". That value can only be used when defining complex types.

253


appliesToEmpty

• The defaultOpenContent element has an optional attribute, appliesToEmpty

• Its value is either true or false.• Its default is false.• It's used to control whether or not extension elements

can be inserted into empty elements:If appliesToEmpty="true" then

extension elements can be inserted into empty elementsElse

extension elements cannot be inserted into empty elements

254


Consider this element with empty content (but it has an attribute):

<element name="image"> <complexType> <attribute name="href" type="anyURI" /> </complexType> </element>

In an instance document we can have this:

<image href="http://wwww.maps.org/boston.gif" />

Now, suppose the image element is declared in a schema that specifies xs:defaultOpenContent with appliesToEmpty="true":

<xs:defaultOpenContent mode="interleave" appliesToEmpty="true"> <xs:any /> </xs:defaultOpenContent>

Then in the instance document I can insert extension elements *within* the <image> element:

<image href="http://wwww.maps.org/boston.gif"> <ex:comment>My home town</ex:comment> </image>

Conversely, if appliesToEmpty="false":

<xs:defaultOpenContent mode="interleave" appliesToEmpty="false"> <xs:any /> </xs:defaultOpenContent>

Then in the instance document I *cannot* insert extension elements within the <image> element.

255


Recall from XSD 1.0 that a complexType may extend or restrict another complexType. Suppose the parent (base) type is open. How does that influence the openness of subtypes? The following slides discusses this. Assume there is no schema-wide xs:defaultOpenContent.

256


Q: Does a subtype inherit its base type's openness?

<openContent>TitleAuthorDate

PublicationType

ISBNPublisher

BookType

extend

This base type has open content

Does this subtype inherit the base type's openness?

257


Q: Does a subtype inherit its base type's openness?

<complexType name="Publication" abstract="true"> <openContent mode="interleave"> <any /> </openContent> <sequence> <element name="Title" type="string" /> <element name="Author" type="string" /> <element name="Date" type="gYear"/> </sequence></complexType>

<complexType name="BookPublication"> <complexContent> <extension base="pub:Publication"> <sequence> <element name="ISBN" type="string"/> <element name="Publisher" type="string"/> </sequence> </extension> </complexContent></complexType>

Open base type

Can extension elements be inserted before and after ISBN and Publisher?


258


A: Yes! Subtypes inherit the openness of its base type

<?xml version="1.0"?><BookStore xmlns="http://www.books.org" xmlns:r="http://www.bookrepository.org" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.books.org BookStore.xsd http://www.bookrepository.org BookRepository.xsd">

<Book> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <r:Binding>Hardcover</r:Binding> <ISBN>1-56592-235-2</ISBN> <Publisher>McMillin Publishing</Publisher> </Book> <Book> <Title>Illusions The Adventures of a Reluctant Messiah</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> <r:Size>5 x 7</r:Size> </Book> <Book> <r:NumPages>299</r:NumPages> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book></BookStore>

Extension elements can be inserted around the base type elements and the subtype elements

Do Lab18

259


Q: Can a subtype turn off the openness of a parent type?

<openContent mode="interleave">TitleAuthorDate

PublicationType

<openContent mode="none">ISBNPublisher

BookType

extend


This subtype specifies that it's not open

260


Q: Can a subtype turn off the openness of a parent type?


<complexType name="BookPublication"> <complexContent> <extension base="pub:Publication"> <openContent mode="none" /> <sequence> <element name="ISBN" type="string"/> <element name="Publisher" type="string"/> </sequence> </extension> </complexContent>/complexType>

Open base type

Closed subtype

Notice that the <openContent> element can be empty

261


Invalid Schema!

• If the base type allows open content, then a type derived from it by extension must also allow open content.

• However, a subtype can turn off openness if it does derive by restriction.


262


Here's how to turn off the openness of a parent type


PublicationType

<openContent mode="none">TitleAuthorDate

BookType

restriction


This subtype specifies that it's not open


263



<complexType name="BookPublication"> <complexContent> <restriction base="pub:Publication"> <openContent mode="none" /> <sequence> <element name="Title" type="string" /> <element name="Author" type="string" /> <element name="Date" type="gYear"/> </sequence> </restriction> </complexContent></complexType>

Notice that the <openContent> element can be empty

Here's how to turn off the openness of a parent type

264


Q: Does a base type inherit the openness of a subtype?

TitleAuthorDate

PublicationType

<openContent>ISBNPublisher

BookType

extend

This subtype has open content

Does this base type inherit the subtype's openness?

265


Q: Does a base type inherit the openness of a subtype?

<complexType name="Publication" abstract="true"> <sequence> <element name="Title" type="string" /> <element name="Author" type="string" /> <element name="Date" type="gYear"/> </sequence></complexType>

<complexType name="BookPublication"> <complexContent> <extension base="pub:Publication"> <openContent mode="interleave"> <any /> </openContent> <sequence> <element name="ISBN" type="string"/> <element name="Publisher" type="string"/> </sequence> </extension> </complexContent></complexType>

Open subtype

Can extension elements be inserted before and after Title, Author, and Date?


266


A: The subtype's openness applies to the base type elements



Extension elements can be inserted around the base type elements as well as the subtype elements

267


Q: Does this subtype have interleave or suffix openness?


PublicationType

<openContent mode="suffix">ISBNPublisher

BookType

extend

This base type specifies interleave openness

This subtype specifies suffix openness

268


Invalid Schema!

• mode="interleave" has more openness than mode="suffix"

• The subtype is trying to reduce the openness of the base type. This is not legal when doing derive by extension.

• However, a subtype can reduce the openness of the base type if it does derive by restriction.

269


Here's how to reduce the openness of a parent type


PublicationType

<openContent mode="suffix">TitleAuthorDate

BookType

restriction


This subtype specifies that extension elements can only be inserted at the bottom (after the <Date> element)


270


Q: Does this subtype have interleave or suffix openness?

<openContent mode="suffix">TitleAuthorDate

PublicationType

<openContent mode="interleave">ISBNPublisher

BookType

extend

This base type specifies suffix openness

This subtype specifies interleave openness


271


A: The subtype has interleave openness



Extension elements can be inserted around the base type elements and the subtype elements

272


Order of openness

interleave is greater than suffix is greater than none

273


Two Rules to Remember

• Derive-by-extension: a subtype cannot specify openness that is less than its parent's openness.

• Derive-by-restriction: a subtype cannot specify openness that is greater than its parent's openness.

274


Derive by extension

A subtype can extend a base type if its openness is greater than or equal to the openness of the base type. The resulting openness is the subtype's openness

none

interleave

extend

OK

none

suffix

extend

OK

interleave

none

extend

interleave

interleave

extend

OK

interleave

suffix

extend

Openness of the Parent Type (i.e. mode="____")

Openness of the Subtype

none

none

extend

OK

275


Derive by extension

suffix

interleave

extend

suffix

suffix

extend

OK

continued

OK



suffix

none

extend

276


Derive by restriction

A subtype can restrict a base type if its openness is less than or equal to the openness of the base type. The resulting openness is the subtype's openness

none

interleave

restrict

none

suffix

restrict

interleave

none

restrict

interleave

interleave

restrict

OK

interleave

suffix

restrict

OK OK



none

none

restrict

277


Derive by restriction

suffix

interleave

restrict

suffix

suffix

restrict

OK

continued



suffix

none

restrict

OK

278


Now let's consider the impact of xs:defaultOpenContent on the openness of a subtype.

279


Two Rules to Remember

• The open content specified on a type wins over the open content specified by xs:defaultOpenContent

• The open content specified by xs:defaultOpenContent wins over the open content inherited by a subtype.

280


Two ways to create interleaved, any-order content

Below are two ways to declare a <Book> element.

Both versions use <all>, to permit the elements within <Book> to occur in any order.

The first version uses an unbounded <any>. The second version uses interleaved open content.

Are these two versions identical? Yes

VERSION #1

<xs:element name="Book"> <xs:complexType> <xs:all> <xs:any minOccurs="0" maxOccurs="unbounded" /> <xs:element name="Author" type="xs:string" /> <xs:element name="Title" type="xs:string" /> <xs:element name="Date" type="xs:string" /> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string" /> </xs:all> </xs:complexType></xs:element>

VERSION #2

<xs:element name="Book"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any /> </xs:openContent> <xs:all> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:all> </xs:complexType></xs:element>

281


Unconstrained Openness

<xs:element name="Book"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any namespace="##any" processContents="skip"/> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>


The extension elements will not be validated because the schema specified processContents="skip"

This means the extension elements can come from any namespace and they will not be validated

282


Constrained Openness

<xs:element name="Book"> <xs:complexType> <xs:openContent mode="interleave"> <xs:any namespace="http://www.repository.org" processContents="strict"/> </xs:openContent> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="Author" type="xs:string" /> <xs:element name="Date" type="xs:string"/> <xs:element name="ISBN" type="xs:string"/> <xs:element name="Publisher" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>


The extension elements will be validated because the schema specified processContents="strict"

This means the extension elements must be validated and they can only come from the repository.org namespace

283


The portion of the DTD for XML Schema 1.1

that pertains to open content

<!ELEMENT schema (include |import | redefine | override | annotation)*, (defaultOpenContent, (annotation)*)?, ((simpleType | complexType | element | attribute |attributeGroup | group | notation ),(annotation)*)* )>

<!ELEMENT defaultOpenContent ((annotation)?, any)><!ATTLIST defaultOpenContent appliesToEmpty (true | false) 'false' mode (interleave | suffix) 'interleave' id ID #IMPLIED>

<!ELEMENT complexType ((annotation)?, (simpleContent | complexContent | openContent?, (all | choice | sequence | group)?), ((attribute | attributeGroup)*, (anyAttribute)?), assert*)>

<!ELEMENT extension ((annotation)?, (openContent?, (all | choice | sequence | group)?)) , ((attribute | attributeGroup)*, (anyAttribute)?), assert*)>

<!ELEMENT restriction ((annotation)?, (openContent?, (all | choice | sequence | group)?)) , ((attribute | attributeGroup)*, (anyAttribute)?), assert*)>

<!ELEMENT openContent ((annotation)?, (any)?)><!ATTLIST openContent mode (none | interleave | suffix) 'interleave' id ID #IMPLIED>

284


ID

http://www.w3.org/TR/2009/CR-xmlschema11-1-20090430/structures.html#cvc-id

285


XML Schema 1.0

In XML Schema 1.0 an element can have only one ID attribute. Thus, this is illegal:

<element name="Widget"> <complexType> <sequence /> <attribute name="SKU" type="ID" /> <attribute name="Model-Num" type="ID" /> </complexType></element>

286


Multiple ID Attributes

In XML Schema 1.1 an element can have multiple attributes of type ID, e.g.,

<Stereo model-number="M459302432" serial-number="S4390200"> …</Stereo>

<element name="Stereo"> <complexType> <sequence> … </sequence> <attribute name="model-number" type="ID" use="required" /> <attribute name="serial-number" type="ID" use="required" /> </complexType></element>

See stereo.xsd in the folder: ID/stereo

287


XML Schema 1.0

For every primitive datatype you can "fix" the value of the element/attribute, e.g.,

<element name="Greeting" type="string" fixed="Hello World" />

The string element Greeting has a fixed (constant) value, "Hello World"

But .... there is one datatype that you can't fix: the ID datatype. Thus, this is illegal:

<attribute name="Food" type="ID" fixed="Popcorn" />

288


ID Attribute with Fixed, Default Value

XML Schema 1.1 allows an ID element to have a fixed value or a default value, e.g.,

<Document version="1.0"> …</Document>

<element name="Document"> <complexType> <sequence> … </sequence> <attribute name= "version" type="ID" fixed="1.0" /> </complexType></element>

289


targetNamespace

http://www.w3.org/TR/xmlschema11-1/#sec-src-element

290


Problem

Suppose that your schema wants to restrict a complexType in another schema. Suppose that other schema has a different targetNamespace.

targetNamespace="http://www.book.org"BookType-Title-Author (unbounded)-Date-ISBN-Publisher

targetNamespace="http://www.bookstore.org"BookTypeMyNamespace-Title-Author (2)-Date-ISBN-Publisher

"restrict"

Book.xsd

Bookstore.xsd

291


targetNamespace="http://www.book.org"BookType-Title-Author (unbounded)-Date-ISBN-Publisher

targetNamespace="http://www.bookstore.org"BookTypeMyNamespace-Title-Author (2)-Date-ISBN-Publisher

"restrict"

Book.xsd

Bookstore.xsd

The Title element here is {http://www.bookstore.org}Title, but it needs to be: {http://www.book.org}Title (recall that the restricted elements must be the same as in the base type). Ditto for the other elements.

292


You cannot solve this problem in XSD 1.0

293


targetNamespace

To solve this problem, in XSD 1.1 you can add a targetNamespace attribute on the element declarations in the subtype:

<xs:import namespace="http://www.book.org" schemaLocation="Book.xsd"/>

<xs:complexType name="BookTypeMyNamespace"> <xs:complexContent> <xs:restriction base="b:BookType"> <xs:sequence> <xs:element name="Title" type="xs:string" targetNamespace="http://www.book.org"/> <xs:element name="Author" type="xs:string" maxOccurs="2" targetNamespace="http://www.book.org"/> <xs:element name="Date" type="xs:gYear" targetNamespace="http://www.book.org"/> <xs:element name="ISBN" type="xs:string" targetNamespace="http://www.book.org"/> <xs:element name="Publisher" type="xs:string" targetNamespace="http://www.book.org"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType>

See the BookStore folder within the targetNamespace folder

Do Lab19

294


targetNamespace on attributes

• You can also add targetNamespace on attribute declarations. <xs:import namespace="http://www.book.org" schemaLocation="Book.xsd"/>

<xs:complexType name="BookTypeMyNamespace"> <xs:complexContent> <xs:restriction base="b:BookType"> <xs:sequence> <xs:element name="Title" type="xs:string" targetNamespace="http://www.book.org"/> <xs:element name="Author" type="xs:string" maxOccurs="2" targetNamespace="http://www.book.org"/> <xs:element name="Date" type="xs:gYear" targetNamespace="http://www.book.org"/> <xs:element name="ISBN" type="xs:string" targetNamespace="http://www.book.org"/> <xs:element name="Publisher" type="xs:string" targetNamespace="http://www.book.org"/> </xs:sequence> <xs:attribute name="id" type="xs:ID" use="required" targetNamespace="http://www.book.org"/> </xs:restriction> </xs:complexContent> </xs:complexType>

The Book.xsd schema declares this attribute, but makes it optional. In this declaration we restrict it to required. See the BookStore folder within the targetNamespace folder

295


redefine

http://www.w3.org/TR/xmlschema11-1/#modify-schema

296


Deprecated

• The XML Schema working group has deprecated the <xs:redefine> element.

• ** Don't use <xs:redefine> any more **

• Reason for deprecation: XSD 1.0 processors implemented conflicting and non-interoperable interpretations of <xs:redefine>

Definition of deprecated (Wikipedia): the term deprecation is applied to software features that are superseded and should be avoided.

297


override

http://www.w3.org/TR/xmlschema11-1/#override-schema

298


Replacement for <redefine>

• The <override> element replaces the <redefine> element.

• With <redefine> you redefined a global type in another schema by extending it or restricting it.

• With <override> you can change a global item in another schema. The change is not restricted to extension/restriction. You can replace the item. The "item" can be an element, attribute, simpleType, complexType, group, or attributeGroup.

299


Example

meeting start-time: time end-time: time room-number: stringcalendar: meeting

office-calendar.xsd

meeting track-id: string speaker: string room-capacity: nonNegativeInteger

conference-calendar.xsd

override meeting

300

Copyright © [2012]. Roger L. Costello. All Rights Reserved. <xs:element name="meeting"> <xs:complexType> <xs:sequence> <xs:element name="start-time" type="xs:time" /> <xs:element name="end-time" type="xs:time" /> <xs:element name="room-number" type="xs:string" /> </xs:sequence> </xs:complexType></xs:element>

<xs:element name="calendar"> <xs:complexType> <xs:sequence> <xs:element ref="meeting" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType></xs:element>

office-calendar.xsd

<xs:override schemaLocation="office-calendar.xsd> <xs:element name="meeting"> <xs:complexType> <xs:sequence> <xs:element name="track-id" type="xs:string" /> <xs:element name="speaker" type="xs:string" /> <xs:element name="room-capacity" type="xs:nonNegativeInteger" /> </xs:sequence> </xs:complexType> </xs:element></xs:override>

conference-calendar.xsd

override meeting <?xml version="1.0" encoding="utf-8"?><calendar>

<meeting> <track-id>XProc</track-id> <speaker>Norm Walsh</speaker> <room-capacity>225</room-capacity> </meeting>

<meeting> <track-id>XSLT</track-id> <speaker>Michael Kay</speaker> <room-capacity>200</room-capacity> </meeting> </calendar>

conference-calendar.xml

conformsto

See the meeting folder within the override folder

Do Lab20

301


substitutionGroup

302


XML Schema 1.0

• XML Schema 1.0 only permitted an element to be substitutable for one element.

• That is, the value of substitutionGroup="___" is one QName.

303


XML Schema 1.1

• XML Schema 1.1 permits an element to be substitutable for multiple elements.

• That is, the value of substitutionGroup="___" is a list of QNames.

304


metrorail subway

metro

substitutable for substitutable for

This is similar to multiple inheritance!

305


<xs:element name="metrorail" type="xs:string" />

<xs:element name="subway" type="xs:string" />

<xs:element name="metro" substitutionGroup="metrorail subway" type="xs:NCName" />

See the substitutionGroup folder, transit subfolder.

306


<xs:element name="X" type="xxx" /> <xs:element name="Y" type="yyy" />

<xs:element name="metro" substitutionGroup="X Y" type="zzz" />

metro's datatype (zzz) must derive from xxx and it must derive from yyy.Thus, if X's datatype is xs:string and metro's datatype is xs:integer, that's an error. If X's datatype is xs:string, Y's datatype is xs:token and metro's datatype is xs:Name, that okay (Name derives from string and token – see next slide)

307


http://www.w3.org/TR/xmlschema11-2/#built-in-datatypes

308


Thanks to Paul Jones for this diagram

309


<xs:element name="X" type="xxx" /> <xs:element name="Y" type="yyy" />

<xs:element name="metro" substitutionGroup="X Y" />

Q: What metro's datatype? xxx or yyy?

Notice that metro does not specify a type.

310


Answer

metro's datatype is the datatype of the first element's datatype in the substitutionGroup list (xxx)

311

Copyright © [2012]. Roger L. Costello. All Rights Reserved. In XML Schema 1.1 you can declare an element to be substitutable for multiple elements, e.g., <element name="Example" substitutionGroup="A B C" ...> Recall that in XML Schema 1.0 if you declared an element and didn't provide a type, then it inherits the type of its head element, e.g., <xs:element name="Subway" type="xs:string" /> <xs:element name="Metro" substitutionGroup="Subway" /> Note that Metro does not specify a type so it inherits Subway's type. Thus the type of Metro is xs:string. But in XML Schema 1.1 there can be multiple head elements, so what type would the element inherit? Example: The Comment element is substitutable for Subway (xs:string), isHardcover (xs:boolean), and TodaysDate (xs:date): <xs:element name="Subway" type="xs:string" /> <xs:element name="Metro" substitutionGroup="Subway" /> <xs:element name="isHardcover" type="xs:boolean" /> <xs:element name="TodaysDate" type="xs:date" /> <xs:element name="Comment" substitutionGroup="Subway isHardcover TodaysDate" /> Also notice that Comment does not specify a type. So what is Comment's data type?

312

Copyright © [2012]. Roger L. Costello. All Rights Reserved. Answer: Comment inherits the data type of the first head element listed. In this case Subway is listed first, so Comment has the xs:string data type. Suppose that Comment was declared like this: <xs:element name="Comment" substitutionGroup=" isHardcover Subway TodaysDate" /> Now isHardcover is listed first, so Comment has the xs:boolean data type. Here is the relevant section from the XML Schema 1.1 specification: An <element> with no referenced or included type definition will correspond to an element declaration which has the same type definition as the *first* substitution-group head named in the substitutionGroup LESSON LEARNED: THE ORDER OF ELEMENTS LISTED IN A SUBSTITUTIONGROUP IS EXTREMELY IMPORTANT.

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explicitTimezone

http://www.w3.org/TR/xmlschema11-2/#rf-explicitTimezone

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New Facet

• Recall that the timezone offset is optional on the datetime datatypes.

• The purpose of this facet is to specify "Hey, you must specify the timezone offset," or "Hey, you must not specify the timezone offset," or "Hey, it's optional whether you specify a timezone offset."

• The value of this facet is one of these: required, prohibited, optional

• This facet is used with these datatypes: datetime, time, date, gYearMonth, gYear, gMonthDay, gDay, gMonth

<simpleType name="event"> <restriction base="datetime"> <explicitTimezone value="required"/> </restriction></simpleType>

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dateTimeStamp

http://www.w3.org/TR/xmlschema11-2/#dateTimeStamp

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New Datatype

• dateTimeStamp is a new data type.

• dateTimeStamp is exactly the same as dateTime, except it requires you to specify the time zone.

<element name="birthdate" type="dateTimeStamp" />---<birthdate>1976-06-21T16:04:00-6:00</birthdate><birthdate>1980-01-01T24:00:00-6:00</birthdate>

This is how to express end-of-day

You must specify the time zone

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Equivalent!

2009-07-29T24:00:00-6:00 The end of the day July 29, 2009

2009-07-30T00:00:00-6:00 The start of the day July 30, 2009

They are two different lexical representations of the same xs:dateTimeStamp value. (Just as "1" and "true" are different lexical representations of the same boolean). So, once converted into the value space, the values theyrepresent are both identical and equal.

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anyAtomicType

http://www.w3.org/TR/xmlschema11-2/#anyAtomicType

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New Datatype

• anyAtomicType is a new data type.

• It is the union of the value spaces of all the primitive types.

• All of the primitive types derive from (constrain) anyAtomicType.

• It has no facets. Thus it cannot be used as the base type in a simpleType.

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<?xml version="1.0"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org" xmlns="http://www.example.org" elementFormDefault="qualified">

<xs:element name="Example"> <xs:complexType> <xs:sequence> <xs:element name="Value" type="xs:anyAtomicType" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:element>

</xs:schema>

<?xml version="1.0"?><Example xmlns="http://www.example.org" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.example.org Example.xsd">

<Value xsi:type="xs:string">Hello World</Value> <Value xsi:type="xs:decimal">12.36</Value> <Value xsi:type="xs:boolean">true</Value></Example>

See Example.xsd in the folder: anyAtomicType/value

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anyAtomicType vs anySimpleTypeConsider these two element declarations:

<element name="A" type="anySimpleType" />

<element name="B" type="anyAtomicType" />

The value of <A> can be any primitive type or a list type, e.g.

<A xsi:type="xs:string">Hello World</A> <A xsi:type="xs:decimal">12.39</A> <A xsi:type="xs:boolean">true</A> <A xsi:type="ex:LotteryNumbers">3 8 19</A>

where ex:LotteryNumbers is defined as a list type:

<xs:simpleType name="LotteryNumbers"> <xs:list itemType="xs:positiveInteger" /> </xs:simpleType>

The value of <B> can only be a primitive type, e.g.

<B xsi:type="xs:string">Hello World</B> <B xsi:type="xs:decimal">12.39</B> <B xsi:type="xs:boolean">true</B>

Thus, the difference between anyAtomicType and anySimpleType is that an anySimpleType value can be a list type, whereas that's not legal for anyAtomicType.

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yearMonthDuration

http://www.w3.org/TR/xmlschema11-2/#yearMonthDuration

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New Datatype

• yearMonthDuration is a new datatype.

• It specifies a duration in terms of year and months, or just months.

• Examples:P1Y3M (a duration of 1 year, 3 months)P15M (a duration of 15 months)

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dayTimeDuration

http://www.w3.org/TR/xmlschema11-2/#dayTimeDuration

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New Datatype

• dayTimeDuration is a new datatype.

• It specifies a duration in terms of day and time, or just time.

• Examples:P35DT01H22M30S (a duration of 35 days,1 hour, 22 minutes, 30 seconds)PT11H (a duration of 11 hours) PT114M (a duration of 114 minutes) PT300S (a duration of 300 seconds)

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The two new duration datatypes were created to satisfy a demand for totally ordered durations, e.g. a duration of 1 month is incomparable with a duration of 30 days -- neither greater than, equal to, nor less than.

Dave Peterson

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Vendor-unique extensions

http://www.w3.org/TR/xmlschema11-2/#idef-idep (see clauses 3 and 4)

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In XSD 1.1, vendors can add their own datatypes and facets.

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Example

A vendor creates a new decimal datatype and a facet that enables you to specify the delimiter used in the decimal:

<xs:simpleType name="money"> <xs:restriction base="vendor:decimal"> <vendor:delimiter value="," /> <xs:restriction></xs:simpleType>

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Conditional Inclusion(a.k.a. Version Control)

http://www.w3.org/TR/xmlschema11-1/#cip

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The Version Control Namespace

http://www.w3.org/2007/XMLSchema-versioning

minVersion

maxVersion

typeAvailable

typeUnavailable

facetAvailable

facetUnavailable

They are attributes.The convention is to use vc: as the prefix.

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Ignored by 1.0 Validators

• The version control attributes are added onto element declarations.

• Since they are in a different namespace they will be ignored by 1.0 validators.

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vc:minVersion, vc:maxVersion

• They are attributes.• They can be added to any element declaration in the

schema.• Their values are decimal.


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Imagine the year is 2030

XML Schemas is now at version 3.2

<element name="Book" vc:minVersion="3.2"> declare the Book element</element>

<element name="Book: vc:minVersion="1.1" vc:maxVersion="3.2"> declare the Book element</element>

a 3.2 validator will use this element declaration

and during pre-processing of the schema, this element declaration will be removed

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1.1 SchemaValidator

3.2 SchemaValidator

<element name="Book" vc:minVersion="3.2"> declare the Book element</element>

<element name="Book: vc:minVersion="1.1" vc:maxVersion="3.2"> declare the Book element</element>

Pre-processing

removes the 1st declaration of Book

removes the 2nd declaration of Book

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Same name, symbol space, Different type, version

• Recall from XSD 1.0: if two element declarations have the same name, are in the same symbol space, and have different types then it is an error.

• Below we see two elements with the same name, in the same symbol space and with different types, but it's not an error because one of them will be removed during pre-processing.

<element name="Book" vc:minVersion="3.2"> declare the Book element</element><element name="Book" vc:minVersion="1.1" vc:maxVersion="3.2"> declare the Book element</element>

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vc:maxVersion is "exclusive"

vc:maxVersion="3.2" means "up to but not including 3.2"

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vc:typeAvailable, vc:typeUnavailable

• They are attributes.

• They can be added to any element declaration in the schema.

• Their values are a list of QNames (a list of namespace-qualified types).

<element name="inStock" vc:typeAvailable="ex:new-datatype" type="ex:new-datatype" />

<element name="inStock" vc:typeUnavailable="ex:new-datatype" type="boolean" />

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<element name="inStock" vc:typeAvailable="ex:new-datatype" type="ex:new-datatype" />

<element name="inStock" vc:typeUnavailable="ex:new-datatype" type="boolean" />

If the validator supports this datatype, it will use this element declaration

If the validator does not support this datatype, it will use this element declaration (<inStock> must be a boolean)

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I Mean the Built-in Datatypes

• The datatypes listed in vc:typeAvailable and vc:typeUnavailable are not user-defined datatypes.

• Rather, they are built-in datatypes.• Suppose vendor X defines a new primitive datatype:

vendor:decimal. The X schema validator will understand it, but other validators won't.

<element name="Size" type="vendor:decimal" vc:typeAvailable="vendor:decimal" />

X SchemaValidator

Other SchemaValidator

Discard

Include

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vc:facetAvailable, vc:facetUnavailable

• They are attributes.

• They can be added to any element declaration in the schema.

• Their values are a list of QNames (a list of namespace-qualified facets).<element name="range" vc:facetAvailable="vendor:delimiter"> <simpleType> <restriction base="decimal"> <vendor:delimiter value="," /> </restriction> </simpleType></element>

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<element name="range" vc:facetAvailable="vendor:delimiter"> <simpleType> <restriction base="decimal"> <vendor:delimiter value="," /> </restriction> </simpleType></element>

<element name="even-integer" vc:facetUnavailable="vendor:delimiter" type="decimal" />

If the validator supports this facet, it will use this element declaration

If the validator does not support this facet, it will use this element declaration

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Relevant, today?

> I'm having a hard time seeing the usefulness of > vc:typeAvailable, vc:typeUnavailable, vc:facetAvailable, > vc:facetUnavailable, vc:minVersion, and vc:maxVersion.> > I can see its usefulness in future versions of XML Schema > (version 1.2, 1.3. etc) but I can't see its usefulness today. > > Does it have any usefulness today? If so, can you give me a > practical example please?

It's mainly there because people realized belatedly that it should have beenin version 1.0. There is some optimism in some quarters that it will beretrofitted to those 1.0 processors that are still under active development,helping users to move forward to 1.1. It has been designed so that it wouldbe conformant to the 1.0 spec to do so.

Michael Sperberg-McQueen

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Factors Influencing an Element Declaration

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Cannot understand an element in isolation

• In XML Schema 1.0 you could examine an element declaration and mostly understand it without consideration of the rest of the schema.– substitutionGroup did require you to examine other parts of the schema

(if the element was global).

• In XML Schema 1.1 an element could be affected by internal and external factors:– one or more alternatives in ancestor elements, and the alternatives may

be using information in inherited attributes– defaultAttributes– vendor-unique capabilities – which version of the XML Schema specification that the validator

implements

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Factors affecting elements

elementdeclaration

alternative

inheritedattribute validator

version

defaultattributes

vendor-unique

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XML Schema

This attribute, start-time, is inheritable

Element declaration

Alternative: If @start-time is before noon then use MorningBeverage

Which schema validator?Which version?

Default attributes

Many non-local factors affect an element declaration

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Identity Constraints and Substitution Elements

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Caution using element substitution: the substituting elements may fail to catch errors in the data Elements substitutable for a head element are required to have types derived from the head element's type, but are not required to enforce the identity constraints of the head element. In other words, the substitutable elements may not validate the same way as the head element. Beware! Example: A BookStore consists of multiple Book elements and each Book element is uniquely identified by its ISBN. Here is an example BookStore: <?xml version="1.0"?><BookStore xmlns="http://www.books.org"> <Book> <Title>Illusions The Adventures of a Reluctant Messiah</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book></BookStore> Note that each ISBN value is unique. We want the XML Schema to enforce that uniqueness.

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Copyright © [2012]. Roger L. Costello. All Rights Reserved. A way to accomplish this is using xsd:key. Let's look at the XML Schema code. BookStore consists of an unbounded number of Book elements: <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Book" maxOccurs="unbounded" /> </xsd:sequence> </xsd:complexType> </xsd:element> Each Book element has a child ISBN element that is required to be unique: <xsd:element name="Book" type="BookType"> <xsd:key name="PK"> <xsd:selector xpath="bk:Book"/> <xsd:field xpath="bk:ISBN"/> </xsd:key> </xsd:element> Here is Book's type definition: <xsd:complexType name="BookType"> <xsd:sequence> <xsd:element name="Title" type="xsd:string" /> <xsd:element name="Author" type="xsd:string" /> <xsd:element name="Date" type="xsd:string" /> <xsd:element name="ISBN" type="xsd:string" /> <xsd:element name="Publisher" type="xsd:string" /> </xsd:sequence> </xsd:complexType>

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Copyright © [2012]. Roger L. Costello. All Rights Reserved. Some of my clients write Fiction books. I would like them to be able to customize their markup a bit. Namely, I would like for them to be able to use the element name "Fiction" rather than "Book". So I declare Fiction to be substitutable for Book: <xsd:element name="Fiction" substitutionGroup="Book" /> My client constructs an XML document using Fiction elements: <?xml version="1.0"?><BookStore xmlns="http://www.books.org"> <Fiction> <Title>Siddhartha</Title> <Author>Hermann Hesse</Author> <Date>1951</Date> <ISBN>0-486-40653-9</ISBN> <Publisher>Dover</Publisher> </Fiction> <Fiction> <Title>Atlas Shrugged</Title> <Author>Ayn Rand</Author> <Date>1957</Date> <ISBN>0-486-40653-9</ISBN> <Publisher>Penguin Books</Publisher> </Fiction></BookStore> Oops! Notice that my client messed up, he mistakenly identified both books by the same ISBN value. XML Schema validation of the document returns "valid". My client has an error in his XML document and it is not being caught by schema validation. Lesson Learned: element substitution is powerful. But without intimate knowledge of the head element, use of your substitution elements may result in XML documents with erroneous data that is not detected by schema validation.

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Constrain Data Types toAvoid Malicious Attacks

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When creating XML Schemas it is important that you restrict the set of allowable characters. Here is a powerful example of how unconstrained strings could be exploited. UNICODE has this character, RIGHT-TO-LEFT OVERRIDE (RLO). It is hex 202E. What the RLO character does is it reverses everything that follows it. For example, gpj.exe is reversed to exe.jpg So, this: ann[RLO]gpj.exe would display as this: annexe.jpg That is, it appears in a displayer as the name of a harmless JPG file, when in fact it is the name of an EXE file. This technique can be (and is being) used to trick users into opening malware executables.

Here’s how: Here’s an XML document that contains the RLO character in the content of the element: <?xml version="1.0"?><Part-of-Czechoslovakia-Annexed-by-Germany> http://www.example.org/ann‮gpj.exe</Part-of-Czechoslovakia-Annexed-by-Germany>

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I dragged that into a browser (Firefox) and here’s what it displayed:

<Part-of-Czechoslovakia-Annexed-by-Germany>http://www.example.org/annexe.jpg</Part-of-Czechoslovakia-Annexed-by-Germany>

It appears that the data is a URL to a harmless JPG file, http://www.example.org/annexe.jpg In fact, the data is a URL to an executable file, http://www.example.org/anngpj.exe Since the data looks good it is incorporated (using an XSLT program) into an HTML document, as a hyperlink. Users then click on the link and … bam! … malware just got loaded onto their machines. You can probably see how the same method could be used to disguise some critical piece of data. Lessons Learned: Avoid using the unconstrained string data type in your XML Schemas.

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Here is an example of a properly constrained element: <xs:element name="Surname" type="English-language-family-name" /> <xs:simpleType name="English-language-family-name"> <xs:annotation> <xs:documentation> The vast majority of English language family names are at least 2 characters long, under 100 characters, and consist of the characters: a-z, A-Z, space, hyphen, period, and apostrophe.</xs:documentation> </xs:annotation> <xs:restriction base="xs:string"> <xs:minLength value="2" /> <xs:maxLength value="100" /> <xs:pattern value="[a-zA-Z' \.-]+" /> </xs:restriction> </xs:simpleType> For more info, see: https://www.google.com/#hl=en&output=search&sclient=psy-ab&q=righttoleftoverride%E2%80%9D+%28RLO%29+character&oq=right&gs_l=hp.3.0.35i39j0l3.1543.2211.0.3556.5.5.0.0.0.1.275.813.0j4j1.5.0...0.0...1c.UpSbwsMBQcQ&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=717d9e3559249a06&biw=1440&bih=742

356


XML Schema quiz on default values

357


Recall that when you declare an element (or attribute) you can give it a default value. For example, I give the Altitude element a default value of 100:

<xs:element name="Altitude" type="xs:integer" default="100" />

In an instance document, if you wish for Altitude to have the default value, then you can simply create it as an empty element: <Altitude></Altitude>

The value of Altitude is 100. Let’s take another example. Here I declare the Title element to be of type string and give it a default value, “Hello World”: <xs:element name="Title" type="xs:string" default="Hello World" />

Now in my instance document I create an empty Title element: <Title></Title>

Quiz: What is the value of Title?

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Answer: the value of Title is the empty string, not the default value. The reason is that the empty string is a valid value of the string data type. If you want Title to have the default value then you must explicitly enter the default value:

<Title>Hello World</Title>

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The answer on the previous slide is not correct. I wrote: > Answer: the value of Title is the empty string, not the default value. > The reason is that the empty string is a valid value of the string data type. The correct answer is: Answer: the value of Title is the default value. The XML Schema specification explains why: An element with a non-empty default value whose simple type definition includes the empty string in its lexical space will nonetheless never receive that empty string value, because the default value will override it.

360


Additional Resources

361


Articles

XML Schema 1.1, Part 1: An introduction to XML Schema 1.1

http://www.ibm.com/developerworks/xml/library/x-xml11pt1/

XML Schema 1.1, Part 2: An introduction to XML Schema 1.1

http://www.ibm.com/developerworks/xml/library/x-xml11pt2/

Documents

1 Copyright © [2012]. Roger L. Costello. All Rights Reserved. XML Schema 1.1 Roger L. Costello 14 December 2012 Structure Specification: