3. Document Type Definitions(DTDs)

3. Document Type Definitions(DTDs)

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Validation

The document must match a declaration in the DTD.

The document satisfies the DTD

then the document is said to be valid.

The DTD lists all the Elements Attributes Entities

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A Simple DTD ExampleDTD Examples :

<! ELEMENT person(name, profession*)>

<! ELEMENT name (first_name, last name)>

<! ELEMENT first_name (#PCDATA)>

<! ELEMENT last_name (#PCDATA)>

<! ELEMENT profession (#PCDATA)>

XML Examples : Valid

<person>

<name>

<first_name>Alan</first_name>

<last_name>Turing</last_name>

</name>

</person>

XML Examples : NOT Valid : omits the name

<person>

<profession> computer scientist</profession>

<profession> mathematician</profession>

<profession> cryptographer</profession>

</person>

XML Examples : NOT Valid : profession elements comes before name

<person>


<name>



</name>

</person>

XML Examples : NOT Valid : add a publication element

<person>

<name>



</name>


<profession> cryptographer</profession>

<publication>On computable Numbers….</publication>

</person>

XML Examples : NOT Valid : add some text outside the allowed children

<person>

<name>



</name>

was a <profession> computer scientist</profession>

a <profession> cryptographer</profession> , and a

</person>

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The Document Type Declaration

The Document Type Declaration

<!DOCTYPE person SYSTEM http://www.cafeconleche.org/dtds/person.dtd>

Internal DTD subsets & External DTD subsets between the brackets is called the internal

DTD come from outside this documents are called

external DTD

Validating a Document XML validation Form : The Brown University Scholarly Tech

nology Group’s

XML well-formedness checker and validator : Richard Tobin

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Element Declarations

In a DTD, XML elements are declared with a DTD element declaration.

Basic form

<!ELEMENT element_name content_specification>

Content_specification Empty elements : EMPTY Elements with only character data : #PCDATA Elements with any contents : ANY Elements with children (sequences) The Number of Children Choice Mixed Content

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Attribute Declarations

A valid document must declare all the element’s attributes.

ATTLIST declarations

A single ATTLIST can declare multiple attributes for a single element type.

<!ATTLIST element-name attribute-name attribute-type default-value>

Example :

<!ATTLIST image source CDATA #REQURED>

width CDATA #REQURED>

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Attribute Type

Value Explanation

CDATA The value is character data

NMTOKEN The value is valid XML name

NMTOKENS

The value is a list of valid XML name

Enumeration

The value is a list of possible values for attribute

ENTITY The value is an entity

ENTITIES The value is a list of entities

ID The value is a unique id

IDREF The value is the id of another element

IDREFS The value is a list of other ids

NOTATION The value is name of notation

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Default value

Type Explanation

Default values The default value of the attribute

#REQUIRED The attribute value must be include in the element

#IMPLIED The attribute does not have to be include

#FIXED The attribute is fixed

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Entities

Entities are storage containers used to hold data.

Entities are variables used to define shortcuts to common text.

The predefines five entities

<(<) , &(&), >(>), "(“), '(‘)

Entities can be declared “internal or external”, “parsed or unparsed”, “general or parameter”.

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Entities

Internal vs. External Parsed vs. Unparsed General vs. Parameter

Type Declared in Used in Always Parsed?

Internal General Internal DTD XML Doc Yes

External General External DTD XML Doc No

Internal Parameter

Internal DTD Internal DTD

Yes

External Parameter

External DTD External DTD

Yes

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External Parsed General Entities

Enable you to store some of your XML document in a separate file, making it reusable across multiple XML documents.

Gives you a chunk of reusable code. Declared in the DTD using an ENTITY declaration.

SYSTEM or PUBLIC

SYSTEM : document containing the contents of the entity is unregistered

PUBLIC : document is registered.

Using External Parsed General Entities

an ampersand(&) and followed by a semicolon(;);

&footer

<!ENTITY Entity_Name SYSTEM “location”>

<!ENTITY Entity_Name PUBIC “location_1” “location_2”>

Example : <!ENTITY footer SYSTEM “http://www.oreilly.com/boilerplate/footer.xml“>

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External Unparsed General Entities

XML parser will not try to parse the entity’s contents. Data within the entity is ignored by the XML parser

and passed to the application that is using the document.

Notations

used by the application to identify the type of data in entity.

<!NOTATION jpeg SYSTEM “image/jpeg”> Declaring an External Unparsed General Entity

<!ENTITY turing_getting_off_bus

SYSTEM http://www.turing.org.uk/turing/pi1/bus.jpg

NDATA jpeg>

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External Unparsed General Entities

Embedding Unparsed Entities in Documents

<!ELEMENT image EMPTY>

<!ATTLIST image source ENTITY #REQUIED>

Using External Unparsed Entities

<image source =“&turing_getting_off_bus”>

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Parameter Entities

Used within the DTD and must “parsed Entity” Using parameter Entities

an percent(%) and followed by a semicolon(;) Example

<!ELEMENT apartment (address, footage, rooms, baths, rent)>

<!ELEMENT sublet (address, footage, rooms, baths, rent)>

<!ELEMENT coop (address, footage, rooms, baths, price)>

<!ELEMENT house (address, footage, rooms, baths, price)><!ENTITY % residential_content “address, footage, rooms, baths”>

<!ENTITY % rental_content “rent”>

<!ENTITY % purchase_content “price”>

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Parameter Entities

<!ELEMENT apartment (%residential_content;, %rental_content;)>

<!ELEMENT sublet (%residential_content;, %rental_content;)>

<!ELEMENT coop (%residential_content;, %purchase_content;)>

<!ELEMENT house (%residential_content;, %purchase_content;)>

<!ELEMENT apartment (address, footage, rooms, baths, rent)>

<!ELEMENT sublet (address, footage, rooms, baths, rent)>

<!ELEMENT coop (address, footage, rooms, baths, price)>

<!ELEMENT house (address, footage, rooms, baths, price)>

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Conditional Inclusion

XML offers the IGNORE directive for the purpose of “commenting out” a section of declaration.

<![ 긴급

[

<!ENTITY 추신 “매우 긴급하오니 반드시 3일내에 답장해 주십시요”

]]>

<![ 보통

[

<!ENTITY 추신 “그럼 답장을 기다리겠습니다 .”>

]]>

<!DOCTYPE 팩스 SYSTEM “ 팩스 .dtd”[

<!ENTITY % 긴급 “ IGNORE”>

<!ENTITY % 보통 “ INCLUDE”>

]>

< 팩스… .>

< 본문 >….

& 추신

</ 본문 >

</ 팩스 >