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5 Document Transformations. XSLT (1.0 W3C Rec. 11/1999; XSLT 2.0 Rec. 1/07) A language for transforming XML documents initial main purpose to support XSL formatting used mainly for independent transformations (esp. XML → HTML) - PowerPoint PPT Presentation
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SDPL 2007 5: Overview of XSLT 1
5 Document Transformations5 Document Transformations
XSLT (1.0 W3C Rec. 11/1999; XSLT (1.0 W3C Rec. 11/1999; XSLT 2.0 Rec. 1/07) XSLT 2.0 Rec. 1/07)
– A language for transforming XML documentsA language for transforming XML documents– initial main purpose to support XSL formattinginitial main purpose to support XSL formatting– used mainly for independent transformationsused mainly for independent transformations
(esp. XML (esp. XML →→ HTML) HTML) Our goal: to understand the basic model and Our goal: to understand the basic model and
central features of XSLTcentral features of XSLT– Overview and an exampleOverview and an example– Data model and processing modelData model and processing model
SDPL 2007 5: Overview of XSLT 2
XSLT: OverviewXSLT: Overview
XSLT uses XML syntax for expressing XSLT uses XML syntax for expressing transformationstransformations– of a document of a document source treesource tree into a into a result treeresult tree
» result and source are result and source are separateseparate trees trees
– by by template rulestemplate rules Each template rule hasEach template rule has
– aa pattern pattern (matched against nodes of the source tree) (matched against nodes of the source tree)– a a template template as a bodyas a body
» instantiated to create fragments of the result treeinstantiated to create fragments of the result tree
SDPL 2007 5: Overview of XSLT 3
Trans form ation P rocess
O utput P ro cess
X M L
T ext
H T M L
S tyleS heet
SourceDocument
Sourc e TreeR esult T ree
Overview of XSLT TransformationOverview of XSLT Transformation
SDPL 2007 5: Overview of XSLT 4
Style Sheets and Template RulesStyle Sheets and Template Rules
AnAn xsl:stylesheetxsl:stylesheet (or(or xsl:transformxsl:transform) ) consists of consists of template rulestemplate rules::<xsl:<xsl:templatetemplate match=" match="PatternPattern">">
TemplateTemplate <!--<!-- well-formed XML!well-formed XML! -->--></xsl:</xsl:templatetemplate>>
Rule applied to nodes of the source tree matched Rule applied to nodes of the source tree matched by the by the PatternPattern – expressed using XPath (XML Path Language)expressed using XPath (XML Path Language)
TemplateTemplate consists of consists of» literal result tree fragments (elements, text), and literal result tree fragments (elements, text), and » XSLT instructions for controlling further processing XSLT instructions for controlling further processing
conventional XSLTconventional XSLTnamespace prefixnamespace prefix
SDPL 2007 5: Overview of XSLT 5
XPath in a NutshellXPath in a Nutshell
XPath 1.0 W3C Rec. 11/99 (2.0 Rec. 1/07)XPath 1.0 W3C Rec. 11/99 (2.0 Rec. 1/07)– a compact non-XML syntax for a compact non-XML syntax for addressing parts of addressing parts of
XML documents XML documents (as (as node-setsnode-sets))– used also in other W3C languagesused also in other W3C languages
» Specs for hyperlinks in XML: Specs for hyperlinks in XML: XLink (Rec. '01) and XPointer (Rec. '03)XLink (Rec. '01) and XPointer (Rec. '03)
» XQuery (Rec. 1/07; extends XPath 2.0)XQuery (Rec. 1/07; extends XPath 2.0)
– also typical operations on also typical operations on strings, numbersstrings, numbers and and truth truth valuesvalues
SDPL 2007 5: Overview of XSLT 6
Early impressions of XSLT 2.0Early impressions of XSLT 2.0
Somewhat more advanced & flexible than 1.0Somewhat more advanced & flexible than 1.0 Complexity of 1.0 vs. 2.0 specs (as pages):Complexity of 1.0 vs. 2.0 specs (as pages):
Data ModelData Model ~ 80 ~ 80
XPath 2.0XPath 2.0 ~100~100
Funcs & opersFuncs & opers ~160~160
XSLT 2.0XSLT 2.0 ~280~280--------------------------------------------------------------------
~620~620
XPath 1.0 ~ 30XPath 1.0 ~ 30
XSLT 1.0 ~ 90XSLT 1.0 ~ 90------------------------------------------------
~ 120~ 120
SDPL 2007 5: Overview of XSLT 7
An XSL transformation exampleAn XSL transformation example
Transform below document to HTML:Transform below document to HTML:
<?xml-stylesheet type="text/xsl" href="walsh.xsl" ?><?xml-stylesheet type="text/xsl" href="walsh.xsl" ?>
<!-- Modified from an example by Norman Walsh --> <!-- Modified from an example by Norman Walsh -->
<doc><title>My Document</title><doc><title>My Document</title>
<para>This is a <em>short</em> document.</para><para>This is a <em>short</em> document.</para>
<para>It only exists to <em>demonstrate a <para>It only exists to <em>demonstrate a
<em>simple</em> XML document</em>.</para><em>simple</em> XML document</em>.</para>
<figure><title>My Figure</title> <figure><title>My Figure</title>
<graphic fileref="myfig.jpg"/></figure><graphic fileref="myfig.jpg"/></figure>
</doc></doc>
SDPL 2007 5: Overview of XSLT 8
Result (edited for readability)Result (edited for readability)
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">Transitional//EN">
<HTML><HEAD><TITLE>A Document</TITLE></HEAD><HTML><HEAD><TITLE>A Document</TITLE></HEAD>
<BODY> <H1><BODY> <H1>My DocumentMy Document</H1></H1>
<P><P>This is a This is a <I><I>shortshort</I></I> document. document.</P></P>
<P><P>It only exists to It only exists to <I><I>demonstrate a demonstrate a <B><B>simplesimple</B></B> XML XML documentdocument</I></I>..</P></P>
<DIV><DIV>
<B>Figure <B>Figure 11. </B> <BR>. </B> <BR>
<IMG src<IMG src="myfig.jpg"="myfig.jpg"><B>><B>My FigureMy Figure</B></B>
</DIV></DIV>
</BODY></BODY>
</HTML></HTML>
SDPL 2007 5: Overview of XSLT 9
Example style sheet beginsExample style sheet begins
<xsl:stylesheet version=<xsl:stylesheet version="1.0""1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/"> <!-- rule for root --><xsl:template match="/"> <!-- rule for root --> <HTML><HEAD><TITLE>A Document</TITLE></HEAD> <HTML><HEAD><TITLE>A Document</TITLE></HEAD> <BODY><BODY> <!-- process root's children here: --><!-- process root's children here: -->
<xsl:apply-templates /> <xsl:apply-templates /> </BODY></BODY> </HTML></HTML> </xsl:template></xsl:template>
<xsl:template match="doc/title"> <xsl:template match="doc/title"> <H1><H1><xsl:apply-templates /><xsl:apply-templates /></H1></H1>
</xsl:template></xsl:template>
SDPL 2007 5: Overview of XSLT 10
Example (Example (paraparass and and emphemphs)s)
<xsl:template match="para"> <xsl:template match="para"> <P><P><xsl:apply-templates /><xsl:apply-templates /></P></P>
</xsl:template> </xsl:template>
<xsl:template match="em"> <xsl:template match="em"> <I><I><xsl:apply-templates /><xsl:apply-templates /></I></I>
</xsl:template> </xsl:template>
<xsl:template match="em/em"> <xsl:template match="em/em"> <B><B><xsl:apply-templates /><xsl:apply-templates /></B></B>
</xsl:template></xsl:template>
SDPL 2007 5: Overview of XSLT 11
Example (Example (figurefigures)s)
<xsl:template match="figure"> <xsl:template match="figure"> <!-- Insert a bold caption of form 'Figure Num. '<!-- Insert a bold caption of form 'Figure Num. '
by counting all figures in the document: --> by counting all figures in the document: --><DIV><B>Figure <DIV><B>Figure <xsl:number level="any" <xsl:number level="any"
count="figure"/>count="figure"/>. </B> . </B> <BR /> <BR /> <!-- Process the children of figure, --><!-- Process the children of figure, --><!-- the 'graphic' child first: --><!-- the 'graphic' child first: --><xsl:apply-templates select="graphic" /> <xsl:apply-templates select="graphic" />
<!-- then the 'title' child: --><!-- then the 'title' child: --><xsl:apply-templates select="title" /> <xsl:apply-templates select="title" />
</DIV></DIV>
</xsl:template> </xsl:template>
SDPL 2007 5: Overview of XSLT 12
Example (end of style sheet)Example (end of style sheet)
<xsl:template match="graphic"> <xsl:template match="graphic"> <IMG src="<IMG src="{@fileref}{@fileref}" />" /> <!-- Assign the value of attribute <!-- Assign the value of attribute
'fileref' to attribute 'src' -->'fileref' to attribute 'src' --> </xsl:template> </xsl:template> <xsl:template match="figure/title"> <xsl:template match="figure/title">
<B> <B> <xsl:apply-templates /><xsl:apply-templates /> </B> </B> </xsl:template></xsl:template>
</xsl:stylesheet></xsl:stylesheet>
SDPL 2007 5: Overview of XSLT 13
Result (edited for readability)Result (edited for readability)
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">Transitional//EN">
<HTML><HEAD><TITLE>A Document</TITLE></HEAD><HTML><HEAD><TITLE>A Document</TITLE></HEAD>
<BODY> <H1><BODY> <H1>My DocumentMy Document</H1></H1>
<P><P>This is a This is a <I><I>shortshort</I></I> document. document.</P></P>
<P><P>It only exists to It only exists to <I><I>demonstrate a demonstrate a <B><B>simplesimple</B></B> XML XML documentdocument</I></I>..</P></P>
<DIV><DIV>
<B>Figure <B>Figure 11. </B> <BR>. </B> <BR>
<IMG src<IMG src="myfig.jpg"="myfig.jpg"><B>><B>My FigureMy Figure</B></B>
</DIV></DIV>
</BODY></BODY>
</HTML></HTML>
SDPL 2007 5: Overview of XSLT 14
What use of XSL(T)?What use of XSL(T)?
XSL can be used in different waysXSL can be used in different ways– for offline document formattingfor offline document formatting
» produce, say, PDF from XML by an XSL style sheet produce, say, PDF from XML by an XSL style sheet (using XSLT + (using XSLT + XSL formatting objectsXSL formatting objects))
– for offline document manipulationfor offline document manipulation» transform XML into other form (XML/HTML/text) transform XML into other form (XML/HTML/text)
using XSLTusing XSLT
– for online document deliveryfor online document delivery» on a Web serveron a Web server» in a Web browser (if the browser supports)in a Web browser (if the browser supports)
SDPL 2007 5: Overview of XSLT 15
XSLT in online document deliveryXSLT in online document delivery
XSLT in a browserXSLT in a browser– defines rendering of XML documentsdefines rendering of XML documents– supported by latest MS and Mozilla browserssupported by latest MS and Mozilla browsers
» transformation of XML to HTML on the fly in browsertransformation of XML to HTML on the fly in browser
XSLT on a Web serverXSLT on a Web server– an HTTP request served by transforming XML on the an HTTP request served by transforming XML on the
fly to HTML (or other format) on the serverfly to HTML (or other format) on the server
SDPL 2007 5: Overview of XSLT 16
Main Aspects of XSLTMain Aspects of XSLT
Data modelData model– How is document data viewed in XSLT?How is document data viewed in XSLT?
Selection mechanismSelection mechanism– How are document parts selected for processing?How are document parts selected for processing?
MatchingMatching– How are the template rules selected?How are the template rules selected?
Processing modelProcessing model– How does the XSLT execution proceed?How does the XSLT execution proceed?
SDPL 2007 5: Overview of XSLT 17
Data Model of XSLT and XPathData Model of XSLT and XPath
Documents are viewed as treesDocuments are viewed as treesmade of seven types of nodes:made of seven types of nodes:– rootroot (additional parent of document element) (additional parent of document element)– elementelement nodes nodes– attributeattribute nodes nodes– texttext nodes nodes– commentscomments, , processing instructionsprocessing instructions and and
namespacesnamespaces NBNB: Entity references are expanded: Entity references are expanded
no entity nodes no entity nodes
SDPL 2007 5: Overview of XSLT 18
XSLT/XPath document treesXSLT/XPath document trees
Defined in Sect. 5 of XPath 1.0 specDefined in Sect. 5 of XPath 1.0 spec– for XSLT/XPath 2.0 & XQuery in their joint Data Model for XSLT/XPath 2.0 & XQuery in their joint Data Model
Element nodes have elements, text nodes, Element nodes have elements, text nodes, comments and processing instructions of their comments and processing instructions of their (direct) (direct) contentcontent as their children as their children– NBNB: attribute nodes are : attribute nodes are notnot children (but have a parent) children (but have a parent)– the the valuevalue of an element node is the concatenation of of an element node is the concatenation of
its text-node descendantsits text-node descendants
SDPL 2007 5: Overview of XSLT 19
XSLT/XPath TreesXSLT/XPath Trees
Similar to the DOM, with slight differences: Similar to the DOM, with slight differences: – 7 vs 12 node types7 vs 12 node types
– value of an element: its full textual content value of an element: its full textual content (In DOM: (In DOM: nullnull))
– no names for text nodes, comment nodes, etc.no names for text nodes, comment nodes, etc.(In DOM: (In DOM: "#text""#text", , "#comment""#comment", etc.) , etc.)
Document orderDocument order of nodes: of nodes:– root node first, otherwise according to the order of the first root node first, otherwise according to the order of the first
character of the XML markup for each nodecharacter of the XML markup for each node
– > element node precedes it's attribute nodes, which precede > element node precedes it's attribute nodes, which precede any content nodes of the elementany content nodes of the element
SDPL 2007 5: Overview of XSLT 20
XSLT/XPath trees: ExampleXSLT/XPath trees: Example
"W ritte n b y the le c ture r."
"W ritte n b y the le c ture r."
root
""
elem ent
"artic le "
text
""
"W ritte n b y "
elem ent
"f ig "
""
text
""
" the le c ture r."
attribute attribute
"cap tio n" "f ile "
"The Lec turer" "p e kka.jp g "
Legend: type
value
nam e
<article>Written by <article>Written by <fig <fig file="pekka.jpg" file="pekka.jpg"
caption="The caption="The Lecturer" /> Lecturer" />
the lecturer.the lecturer.</article></article>
33rdrd
55thth or 6 or 6thth
11stst
55thth or 6 or 6thth
77thth
44thth
22ndnd
nullnull in DOM in DOM
SDPL 2007 5: Overview of XSLT 21
Main Aspects of XSLTMain Aspects of XSLT
Data modelData model Selection mechanismSelection mechanism
– How are document parts selected for How are document parts selected for processing?processing?
– A: With XPath expressionsA: With XPath expressions MatchingMatching Processing modelProcessing model
SDPL 2007 5: Overview of XSLT 22
XPath ExpressionsXPath Expressions
Used for selecting source tree nodes, conditional Used for selecting source tree nodes, conditional processing, and generating new text contentprocessing, and generating new text content– return return node-sets, truth values, numbers node-sets, truth values, numbers oror strings strings– can select any parts of source tree (can select any parts of source tree (node-setnode-set) for ) for
processing, using … processing, using … Location pathsLocation paths
– the most characteristic of XPath expressionsthe most characteristic of XPath expressions– evaluated with respect to a evaluated with respect to a context nodecontext node
» often the often the current nodecurrent node matched by the template pattern matched by the template pattern
– resultresult: set of nodes selected by the location path: set of nodes selected by the location path
SDPL 2007 5: Overview of XSLT 23
Location pathsLocation paths
Consist of Consist of location stepslocation steps separated by ' separated by '//''– each step produces a set of nodeseach step produces a set of nodes– steps evaluated left-to-right, steps evaluated left-to-right,
each node in turn as context nodeeach node in turn as context node» path begins with ‘path begins with ‘//’ ’ root is the first context node root is the first context node
Complete location step: Complete location step: AxisNameAxisName:::: NodeTestNodeTest ( ([[PredicateExprPredicateExpr]])*)*
– axisaxis specifies the tree relationship between the context specifies the tree relationship between the context node and the selected nodes node and the selected nodes
– node testnode test restricts the type and and name of nodes restricts the type and and name of nodes– filtered further by 0 or more filtered further by 0 or more predicatespredicates
SDPL 2007 5: Overview of XSLT 24
Location steps: AxesLocation steps: Axes
In total 13 axes (~ directions in tree)In total 13 axes (~ directions in tree)– for staying at the context node:for staying at the context node:
» selfself
– for going downwards:for going downwards:» childchild, , descendantdescendant, , descendant-or-selfdescendant-or-self
– for going upwards:for going upwards:» parentparent, , ancestorancestor, , ancestor-or-selfancestor-or-self
– for moving towards start/end of the document:for moving towards start/end of the document:» preceding-siblingpreceding-sibling, , following-siblingfollowing-sibling, , precedingpreceding, , followingfollowing
– ““Special” axesSpecial” axes» attributeattribute, , namespacenamespace
SDPL 2007 5: Overview of XSLT 25
XPath Axes and Their OrientationXPath Axes and Their Orientation
Ordinary axes oriented away from context nodeOrdinary axes oriented away from context node((attributeattribute and and namespacenamespace axes are unordered) axes are unordered)– the the position()position() for the closest node for the closest node = 1= 1– for the most remote node, for the most remote node, position() = last()position() = last()
1
C o nte xtno de :
The simplest axis,The simplest axis, self::self::
SDPL 2007 5: Overview of XSLT 26
XPath Axes and Their OrientationXPath Axes and Their Orientation
parent::parent:: (exists for every node except the root)(exists for every node except the root)
1
Context node:
SDPL 2007 5: Overview of XSLT 27
XPath Axes and Their OrientationXPath Axes and Their Orientation
ancestor::ancestor:: 2
1
ancestor-or-self::ancestor-or-self::3
2
1
SDPL 2007 5: Overview of XSLT 28
XPath Axes and Their OrientationXPath Axes and Their Orientation
child::child::
431 2
C ontextnode :
SDPL 2007 5: Overview of XSLT 29
XPath Axes and Their OrientationXPath Axes and Their Orientation
descendant::descendant::
871 4
2 3 65 9
descendant-or-self::descendant-or-self:: 1
982 5
3 4 76 1 0
SDPL 2007 5: Overview of XSLT 30
XPath Axes and Their OrientationXPath Axes and Their Orientation
preceding-sibling::preceding-sibling::
2 1
following-sibling::following-sibling::
21
SDPL 2007 5: Overview of XSLT 31
XPath Axes and Their OrientationXPath Axes and Their Orientation
following::following::
21
3
4
5
preceding::preceding::
3
2 1
SDPL 2007 5: Overview of XSLT 32
Location paths: Node testsLocation paths: Node tests
Node tests (slightly simplified)Node tests (slightly simplified)– NameName: any : any elementelement node with name node with name NameName
(on an attribute axis, any attribute node with name (on an attribute axis, any attribute node with name NameName))
– **: any : any elementelement (any (any attributeattribute node on an attribute axis) node on an attribute axis)
– text()text(): any text node: any text node» comment()comment(): any comment node: any comment node» processing-instruction()processing-instruction(): any processing instruction: any processing instruction
– node()node(): any node of any type: any node of any type
SDPL 2007 5: Overview of XSLT 33
Location paths: AbbreviationsLocation paths: Abbreviations
Abbreviations in location stepsAbbreviations in location steps– ''child::child::'' can be omitted can be omitted– ''attribute::attribute::'' can be shortened to can be shortened to ''@@''– ''self::node()self::node()'' can be shortened to can be shortened to ''..'' (period)(period)– ''parent::node()parent::node()'' can be shortened to can be shortened to ''....''
– Predicate 'Predicate '[position()=[position()=nn]]' for testing occurrence ' for testing occurrence position position nn can be shortened to ' can be shortened to '[[nn]]''
– ''/descendant-or-self::node()//descendant-or-self::node()/'' shortened to shortened to ''////''
Syntax resembles slightly Linux/Unix file path namesSyntax resembles slightly Linux/Unix file path names
SDPL 2007 5: Overview of XSLT 34
Semantics of Location Paths (example)Semantics of Location Paths (example)
{2, 5, 7}{2, 5, 7}
AA
BB
context nodecontext node
CC"txt""txt"AA BB
BBCC55
884433
22
11
66
77
*/node()/parent::B[child::A]*/node()/parent::B[child::A]
{3, 4, 6, 8}{3, 4, 6, 8} {2, 5, 7}{2, 5, 7}
final value: {2}final value: {2}
value after value after each step:each step:
SDPL 2007 5: Overview of XSLT 35
Location path examples (1)Location path examples (1)
chapchap children of current node:children of current node: ../chap/chap (or simply (or simply chapchap, or, or ./child::*[name()='chap']./child::*[name()='chap']))
The document element The document element (child element of root node):(child element of root node): /*/*
Elements Elements chapterchapter anywhere (below the root): anywhere (below the root): //chapter//chapter (( .//chapter.//chapter anywhere below anywhere below
the context node)the context node) All All chapterchapters ofs of typetype AA oror BB: :
//chapter[@type='A' or @type='B']//chapter[@type='A' or @type='B'] the previousthe previous chapterchapter siblingsibling: :
preceding-sibling::chapter[1]preceding-sibling::chapter[1]
SDPL 2007 5: Overview of XSLT 36
Location path examples (2)Location path examples (2)
All child elements having an attributeAll child elements having an attribute typetype: : *[@type]*[@type]
NBNB: Node sets as truth values: empty - : Node sets as truth values: empty - falsefalse; non-empty - ; non-empty - truetrue
All child elements of any All child elements of any authorauthor child: child: author/*author/*
sectsections whoseions whose typetype attribute equals attribute equals stylestyle attribute of the document element:attribute of the document element:
//sect[@type = /*/@style]//sect[@type = /*/@style] First First authorauthor child, and previous to the last: child, and previous to the last:
author[1], author[last()-1]author[1], author[last()-1]
SDPL 2007 5: Overview of XSLT 37
Main Aspects of XSLTMain Aspects of XSLT
Data modelData model Selection mechanismSelection mechanism MatchingMatching
– How are the rules selected?How are the rules selected?– A: With A: With PatternsPatterns
Processing modelProcessing model
SDPL 2007 5: Overview of XSLT 38
XSLT PatternsXSLT Patterns
Main use in match attributes of template rules:Main use in match attributes of template rules:<xsl:template match="<xsl:template match="PatternPattern">">
also used for numbering (Which parts are counted?)also used for numbering (Which parts are counted?)
Restricted location path expressions:Restricted location path expressions:– steps with steps with childchild and and attributeattribute axes only, axes only,
separated byseparated by ' '////' ' or or ''//''» but arbitrary predicates in but arbitrary predicates in [[ExprExpr]] allowedallowed
– may begin withmay begin with id(id(''IdValIdVal''))(for selecting element nodes by ID attribute values)(for selecting element nodes by ID attribute values)
– alternative patterns separated by 'alternative patterns separated by '||' ' ((~ ~ node-set union)node-set union)
SDPL 2007 5: Overview of XSLT 39
XSLT Patterns: SemanticsXSLT Patterns: Semantics
A location path pattern A location path pattern PP is of form is of form StepStep11 StepStep22 …… StepStepnn-1 -1 StepStepn n ,,
where each separator where each separator is either ` is either `//´ or `´ or `////´ ´ – may also begin with ‘may also begin with ‘//’’; ; Pattern Pattern ‘‘//’’ matchesmatches only the root only the root
ElseElse P P matches a nodematches a node vvnn iff there are nodes iff there are nodes vvnn,..., ,..., vv11 such such
that each that each vvii satisfies the node test and possible predicates satisfies the node test and possible predicates
of of StepStepi i , and which form a path towards the root:, and which form a path towards the root:
– If If P P begins with a single ‘begins with a single ‘//’, node ’, node vv11 must be child of the must be child of the
rootroot
– in case of in case of StepStepii-1-1//StepStepi i node node vvi-1 i-1 is the is the parentparent of of vvii
– in case of in case of StepStepii-1-1////StepStepi i node node vvi-1i-1 is an is an ancestorancestor of of vvii
SDPL 2007 5: Overview of XSLT 40
XSLT Patterns: ExamplesXSLT Patterns: Examples
match="sect-head | section/head"match="sect-head | section/head"– matches any element with namematches any element with name sect-headsect-head, and any, and any headhead elements directly below aelements directly below a sectionsection
PatternPattern /appendix//ulist/item[1]/appendix//ulist/item[1]
matches the first matches the first itemitem element in aelement in a ulistulist which is which is contained in ancontained in an appendixappendix, which is the document , which is the document elementelement
SDPL 2007 5: Overview of XSLT 41
Main Aspects of XSLTMain Aspects of XSLT
Data modelData model Selection mechanismSelection mechanism MatchingMatching Processing modelProcessing model
– How does the XSLT execution proceed?How does the XSLT execution proceed?
SDPL 2007 5: Overview of XSLT 42
XSLT Processing ModelXSLT Processing Model
0. Parse the document into a 0. Parse the document into a source treesource tree
1. Construct the 1. Construct the result treeresult tree by applying by applying template rulestemplate rules to the source tree to the source tree
2. Serialize the result tree 2. Serialize the result tree (as XML, HTML or text)(as XML, HTML or text)
SDPL 2007 5: Overview of XSLT 43
Trans form ation P rocess
O utput P ro cess
X M L
T ext
H T M L
S tyleS heet
SourceDocument
Sourc e TreeR esult T ree
Overview of XSLT TransformationOverview of XSLT Transformation
SDPL 2007 5: Overview of XSLT 44
Result Tree Construction (roughly)Result Tree Construction (roughly)
ResultTree:= ApplTempls([root of the source tree]);ResultTree:= ApplTempls([root of the source tree]);
procproc ApplTempls(CNL: ApplTempls(CNL: list of list of Nodes) Nodes) returns list of returns list of Nodes:Nodes:
ResList:= emptyNodeList();ResList:= emptyNodeList();
for eachfor each Node cn Node cn inin CNL CNL do do // // current node current node in in current node listcurrent node list
Find matching template rule (of highest Find matching template rule (of highest prioritypriority; See next); See next)
Instantiate its template T in context (cn, CNL), and add to ResList; Instantiate its template T in context (cn, CNL), and add to ResList; Replace each Replace each <apply-templates select="<apply-templates select="EE"/>"/> in T by in T by ApplTempls(L), where L = value of expr E in context (cn, CNL);ApplTempls(L), where L = value of expr E in context (cn, CNL);
end forend for;;
returnreturn ResList; ResList;
SDPL 2007 5: Overview of XSLT 45
Selecting one of matching rulesSelecting one of matching rules
Priority of a rule can be specified explicitly: Priority of a rule can be specified explicitly: <xsl:template priority="2.0"<xsl:template priority="2.0" … …
Default priorities based on the Default priorities based on the matchmatch pattern: pattern:– 0 for simple name tests 0 for simple name tests (like (like parapara, , @href@href))– negative for less specific patterns negative for less specific patterns
e.g., e.g., **, , @*@*, , node()node()– 0.5 for more complex patterns0.5 for more complex patterns
Multiple matching rules with the same maximum Multiple matching rules with the same maximum priority is an error - Processor may (quietly!) priority is an error - Processor may (quietly!) choose the choose the last onelast one of them of them
SDPL 2007 5: Overview of XSLT 46
Application of template rulesApplication of template rules
Without a Without a selectselect attribute (attribute (~ ~ select="node()"select="node()")) <xsl:apply-templates /><xsl:apply-templates />
processes all children of current nodeprocesses all children of current node– > “> “default traversaldefault traversal””: top-down : top-down
Selected nodes are processed in Selected nodes are processed in document order document order (if not (if not sorted with sorted with xsl:sortxsl:sort))
Built-in rulesBuilt-in rules support the top-down traversal if no support the top-down traversal if no matching rules are foundmatching rules are found
SDPL 2007 5: Overview of XSLT 47
Built-In Default RulesBuilt-In Default Rules
For the root and element nodes:For the root and element nodes: <xsl:template match="/ | *"> <xsl:template match="/ | *">
<xsl:apply-templates /> <xsl:apply-templates /> </xsl:template></xsl:template>
For text and attribute nodes:For text and attribute nodes:<xsl:template match="text() | @*"><xsl:template match="text() | @*"><!-- Insert the string value <!-- Insert the string value
of current node: --> of current node: --> <xsl:<xsl:value-ofvalue-of select="." /> select="." />
</xsl:template></xsl:template> Low priorityLow priority can be overriddencan be overridden
SDPL 2007 5: Overview of XSLT 48
A (Tricky) Processing Example A (Tricky) Processing Example
Consider transforming documentConsider transforming document<A><A><B>b1</B><C>cc<B>b2</B></C><D>dd</D><B>b3</B><B>b1</B><C>cc<B>b2</B></C><D>dd</D><B>b3</B></A></A>
with the below rules:with the below rules:<xsl:template match="/"> <!-- Rule 1 --><xsl:template match="/"> <!-- Rule 1 -->
<R><R><xsl:apply-templates select="//C" /><xsl:apply-templates select="//C" /></R></R></xsl:template></xsl:template>
<xsl:template match="C"> <!-- Rule 2 --><xsl:template match="C"> <!-- Rule 2 --><NewC>New:<NewC>New: <xsl:apply-templates select="../B" /> <xsl:apply-templates select="../B" />
<xsl:apply-templates /> <xsl:apply-templates /> </NewC></NewC>
</xsl:template></xsl:template>
SDPL 2007 5: Overview of XSLT 49
Processing example (2)Processing example (2)
The resultThe result<R><NewC><R><NewC>New:New: b1b3ccb2</NewC></R> b1b3ccb2</NewC></R>
is obtained as follows: is obtained as follows: 1. 1. Rule 1 matches the root node Rule 1 matches the root node Element node Element node RR is added is added
to the result; Instruction to the result; Instruction <xsl:apply-templates <xsl:apply-templates
select="//C" />select="//C" /> selects the (only)selects the (only) CC element for element for processing (which will produce the contents of node processing (which will produce the contents of node RR). ).
2. 2. Rule 2 with patternRule 2 with pattern "C""C" creates into result tree acreates into result tree a NewCNewC element node with text node element node with text node "New: ""New: " as its first child.as its first child.
SDPL 2007 5: Overview of XSLT 50
Processing example (3)Processing example (3)
3. Instruction 3. Instruction <xsl:apply-templates select="../B" /><xsl:apply-templates select="../B" /> selects element selects element BB siblings of current node (siblings of current node (CC). The built-in ). The built-in element rule applies to these, and the built-in text rule to element rule applies to these, and the built-in text rule to their children. their children. Result: text nodesResult: text nodes "b1""b1" and and "b3""b3" become the next become the next children ofchildren of NewCNewC..
4. Instruction 4. Instruction <xsl:apply-templates /><xsl:apply-templates /> in the context of in the context of element node element node CC selects its children, selects its children, "cc""cc" and and <B>b2</B><B>b2</B>, for processing. The built-in text rule inserts , for processing. The built-in text rule inserts value value "cc""cc" to the result tree, and the to the result tree, and the BB element element node node becomesbecomes "b2""b2" in the result (similarly to step 3). in the result (similarly to step 3).
SDPL 2007 5: Overview of XSLT 51
Processing example (4)Processing example (4)
AA
BB BB
BB
CC DD
b1b1
SourceSource ResultResult
cccc
b2b2
dddd
RR
NewCNewC
New: New: b3b3
1.1.2.2.
3.3.
4.4.
b3b3b1b1 cccc b2b2
SDPL 2007 5: Overview of XSLT 52
Is it Really So Tricky?Is it Really So Tricky?
Seldom, fortunatelySeldom, fortunately– but a computer scientist wants to understand how a but a computer scientist wants to understand how a
model worksmodel works Often sufficient to give simple declarative rules for Often sufficient to give simple declarative rules for
different cases, likedifferent cases, like<xsl:template match="<xsl:template match="parapara"> ">
<P><P><xsl:apply-templates /><xsl:apply-templates /></P></P> </xsl:template></xsl:template>