SDPL 2007XSLT: Additional Features and Computing1 5.1 Additional Features n XPath for arithmetics, cross-references, and string manipulation n Generating

SDPL 2007 XSLT: Additional Features and Computing

1

5.1 Additional Features 5.1 Additional Features

XPath for arithmetics, cross-references, and XPath for arithmetics, cross-references, and string manipulation string manipulation

Generating textGenerating text– for contentfor content– for attribute valuesfor attribute values

Repetition, sorting and conditional processingRepetition, sorting and conditional processing Numbering document contentsNumbering document contents

5.2 Computing with XSLT 5.2 Computing with XSLT


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XPath: ArithmeticsXPath: Arithmetics

Double-precision floating-point operators Double-precision floating-point operators ++, , --, , **, , divdiv, , modmod (same as (same as %% in Java)in Java)

» e.g. e.g. 2.3 mod 1.12.3 mod 1.1 ≈ 0.1≈ 0.1 Rounding numbers up, down, and to the closest integer:Rounding numbers up, down, and to the closest integer:

floor(x)floor(x), , ceiling(x)ceiling(x),,round(x)round(x) Formatting numbers as strings (e.g.):Formatting numbers as strings (e.g.):

» format-number(-1.2534, format-number(-1.2534, ""0.00.0"") = ) = ""-1.3-1.3""

– XSLTXSLT 1.0 function; uses Java decimal format patterns 1.0 function; uses Java decimal format patterns


3

Aggregate FunctionsAggregate Functions

Counting nodes Counting nodes » count(count(node-setnode-set))

– and summing them as numbers and summing them as numbers » sum(sum(node-setnode-set))

Example: Example: – Average of observed temps below current node:Average of observed temps below current node:sum(sum(.//obs/@temperature.//obs/@temperature))

divdiv count( count(.//obs.//obs))


4

Cross-referencingCross-referencing

Function Function idid selects elements by their unique IDselects elements by their unique ID– NBNB: ID attributes must be declared in DTD: ID attributes must be declared in DTD

(See an example later)(See an example later)

Examples:Examples:– id('sect:intro')id('sect:intro')

selects the element with unique IDselects the element with unique ID ""sect:introsect:intro""– id('sect:intro')/auth[3]id('sect:intro')/auth[3]

selects the thirdselects the third authauth of the above elementof the above element– id('sect1 sect2 sect3')id('sect1 sect2 sect3')selects 3 sections selects 3 sections

(with corresponding ID values)(with corresponding ID values)


5

String manipulationString manipulation

Equality and inequality of strings with Equality and inequality of strings with operatorsoperators == andand !=!=– "foo" = 'foo'"foo" = 'foo'; ; (NB alternative quotes)(NB alternative quotes)– "foo" != "Foo""foo" != "Foo"

Testing for substrings:Testing for substrings:– starts-with("starts-with("dogdogbert", "bert", "dogdog") = true()") = true()– contains("docontains("dogbegbert", "rt", "gbegbe") = true()") = true()

Concatenation (of two or more strings), Concatenation (of two or more strings), – concat("dog", "bert") = "dogbert"concat("dog", "bert") = "dogbert"


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XPath: more string functionsXPath: more string functions

– substring-before("ftp:substring-before("ftp:////a", "a", "////") = ") = substring-before("ftp:substring-before("ftp:///a", "/a", "//") = "ftp:"") = "ftp:"

– substring-after("ftp:substring-after("ftp:///a", "/a", "//")= "/a"")= "/a"– string-length("dogbert")=7string-length("dogbert")=7– substring(substring(string, start, length?string, start, length?):):

» substring("dogbert", 1, 3) = "dog"substring("dogbert", 1, 3) = "dog"» substring("dogbert", 3) = "gbert"substring("dogbert", 3) = "gbert"

– translate(translate(Str, Replaced, ReplacingStr, Replaced, Replacing):):» translate("translate("doggdoggy","y","dgodgo","Ssi") = "Sissy"","Ssi") = "Sissy"


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Generating TextGenerating Text

Insert text nodes with a computed value in the result:Insert text nodes with a computed value in the result:<<xsl:value-ofxsl:value-of select=" select="ExprExpr" />" />

– if if ExprExpr gives a node-set, the gives a node-set, the value of the first nodevalue of the first node in in document order is used (in XSLT 2.0 all, space-separated)document order is used (in XSLT 2.0 all, space-separated)

Example: Transform elements likeExample: Transform elements like

<name alias="Bird"><name alias="Bird"><first>Charlie</first><last>Parker</last><first>Charlie</first><last>Parker</last>

</name></name>

to the formto the form

Charlie Charlie ("("BirdBird")") Parker Parker


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Computing generated text (2)Computing generated text (2)

This can be specified by template ruleThis can be specified by template rule<xsl:template match="name"><xsl:template match="name"><xsl:<xsl:value-ofvalue-of select="first" /> select="first" />("("<xsl:<xsl:value-ofvalue-of select="@alias" /> select="@alias" />")") <xsl:<xsl:value-ofvalue-of select="last" /> select="last" /> <xsl:text><xsl:text></xsl:text></xsl:text></xsl:template></xsl:template>

Verbatim text (like the white-space above) can be Verbatim text (like the white-space above) can be inserted usinginserted using xsl:textxsl:text


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Attribute value templatesAttribute value templates

The string-value of an expression can be inserted The string-value of an expression can be inserted in an attribute value by surrounding the in an attribute value by surrounding the expression by bracesexpression by braces {{ andand }}

Example: Transform source elementExample: Transform source element<photo><photo>

<file><file>Mary.jpgMary.jpg</file></file> <size width="300"/><size width="300"/>

</photo></photo>into forminto form

<img src="/images/<img src="/images/Mary.jpgMary.jpg" " width="300" />width="300" />


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Attribute value templates (2)Attribute value templates (2)

This can be specified by template ruleThis can be specified by template rule<xsl:template match="photo"><xsl:template match="photo">

<img src="/images/<img src="/images/{file}{file}""width="width="{size/@width}{size/@width}" />" />

</xsl:template></xsl:template> ExpressionsExpressions {file}{file} andand {size/@width}{size/@width} are are

evaluated in the context of the current node (the evaluated in the context of the current node (the photophoto element)element)


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XSLT: RepetitionXSLT: Repetition

Nodes can be "pulled" from source for Nodes can be "pulled" from source for processing using processing using

<<xsl:for-eachxsl:for-each select=" select="ExprExpr">">TemplateTemplate

</</xsl:for-eachxsl:for-each>>

– TemplateTemplate is applied to the selected nodelist, is applied to the selected nodelist, each node in turn as the each node in turn as the current()current() node node» in document order, unless sorted using in document order, unless sorted using xsl:sortxsl:sort

instructions (see later)instructions (see later)


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Example (of Example (of for-eachfor-each))

Format the below document as HTML:Format the below document as HTML:<!DOCTYPE document [ <!ATTLIST section id ID #IMPLIED> ]><!DOCTYPE document [ <!ATTLIST section id ID #IMPLIED> ]><document> <title>The Joy of XML</title> <document> <title>The Joy of XML</title> <section id="Intro"><title>Getting Started</title> <section id="Intro"><title>Getting Started</title> <name><first>Helen</first> <last>Brown</last></name> <name><first>Helen</first> <last>Brown</last></name> says that processing XML documents is fun. says that processing XML documents is fun. <name><first>Dave</first> <last>Dobrik</last></name> agrees. <name><first>Dave</first> <last>Dobrik</last></name> agrees. </section> </section> <section><title>Family affairs</title> <section><title>Family affairs</title> <name><first>Bob</first> <last>Brown</last></name> is the <name><first>Bob</first> <last>Brown</last></name> is the husband of <name><first>Helen</first> husband of <name><first>Helen</first> <last>Brown</last></name>. </section> <last>Brown</last></name>. </section> <section><title>Finishing Up</title> <section><title>Finishing Up</title> As we discussed in <title-ref idref="Intro" />, processing XML As we discussed in <title-ref idref="Intro" />, processing XML documents is fun. </section></document>documents is fun. </section></document>


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Example: Table of contentsExample: Table of contents

A table of contents can be formed of section titles:A table of contents can be formed of section titles:<xsl:template match="/"><xsl:template match="/"><HTML><HEAD> <TITLE><xsl:value-of <HTML><HEAD> <TITLE><xsl:value-of

select="document/title"/></TITLE></HEAD> select="document/title"/></TITLE></HEAD> <BODY> <BODY> <H2>Table of Contents</H2> <H2>Table of Contents</H2> <OL>  <OL>  <xsl: <xsl:for-eachfor-each select="//section/title"> select="//section/title"> <LI><xsl:apply-templates /></LI> <LI><xsl:apply-templates /></LI> </xsl: </xsl:for-eachfor-each>> </OL>  </OL>  <xsl:apply-templates select="document/section"/> <xsl:apply-templates select="document/section"/>

</BODY> </HTML> </BODY> </HTML></xsl:template></xsl:template>


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Example (cont; Cross references)Example (cont; Cross references)

Cross-refs can also be processed usingCross-refs can also be processed using for-eachfor-each: : <xsl:template match="title-ref"> <xsl:template match="title-ref"> <xsl:for-each select="id(@idref)"> <xsl:for-each select="id(@idref)">  Section (<xsl:value-of Section (<xsl:value-of

select="substring(title, 1, 8)" />...)select="substring(title, 1, 8)" />...) </xsl:for-each></xsl:for-each></xsl:template></xsl:template>

With this rule the source fragment With this rule the source fragment As we discussed in <title-ref idref="Intro"/>As we discussed in <title-ref idref="Intro"/>

becomesbecomesAs we discussed in Section (Getting …)As we discussed in Section (Getting …)


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XSLT SortingXSLT Sorting

A sorted order for the processing of nodes with A sorted order for the processing of nodes with xsl:for-xsl:for-eacheach andand xls:apply-templatesxls:apply-templates can be specified bycan be specified by <<xsl:sortxsl:sort/>/>

controlled by attributes ofcontrolled by attributes of xsl:sortxsl:sort, like, like– selectselect: expression for the sort key (default: : expression for the sort key (default: ".""."))– data-typedata-type: : "text""text" (default) or(default) or "number""number" – orderorder:: "ascending""ascending" (default) (default)

or or "descending""descending" The first The first xsl:sortxsl:sort specifies the primary sort key, specifies the primary sort key,

the second one the secondary sort key, and so on.the second one the secondary sort key, and so on.


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Example (cont; Sorted index of names)Example (cont; Sorted index of names)

All names can be collected in a last-name-first-name order All names can be collected in a last-name-first-name order using the below templateusing the below template<H2>Index</H2> <UL><H2>Index</H2> <UL> <xsl:for-each select="//name"> <xsl:for-each select="//name"> < <xsl:sortxsl:sort select="last" /> select="last" /> < <xsl:sortxsl:sort select="first" /> select="first" /> <LI><xsl:value-of select="last" <LI><xsl:value-of select="last" />, <xsl:value-of select="first"/></LI> />, <xsl:value-of select="first"/></LI> </xsl:for-each> </xsl:for-each></UL></UL>

This creates an UL list with itemsThis creates an UL list with items<LI>Brown, Bob</LI> <LI>Brown, Bob</LI> <LI>Brown, Helen</LI> <LI>Brown, Helen</LI> <LI>Brown, Helen</LI> <LI>Brown, Helen</LI> <LI>Dobrik, Dave</LI><LI>Dobrik, Dave</LI>

Possible to eliminate duplicates?Possible to eliminate duplicates?Yes, but a bit tricky. See nextYes, but a bit tricky. See next


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Conditional processingConditional processing

A template can be instantiated or ignored withA template can be instantiated or ignored with<xsl:if<xsl:if test="test="BooleanExprBooleanExpr">">

TemplateTemplate</xsl:if></xsl:if>

Example: a comma-separated list of names:Example: a comma-separated list of names:<xsl:template match="namelist/name"><xsl:template match="namelist/name"> <xsl:apply-templates/> <xsl:apply-templates/> < <xsl:ifxsl:if test="test="position() < last()position() < last()"" > >,, </</xsl:ifxsl:if>></xsl:template></xsl:template>


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An aside: Meaning of An aside: Meaning of position()position()

Evaluation wrt the current node list. The above applied to Evaluation wrt the current node list. The above applied to

<namelist><name>a</name><name>b</name></namelist> <namelist><name>a</name><name>b</name></namelist> <namelist><name>c</name><name>d</name></namelist><namelist><name>c</name><name>d</name></namelist>

by invocationby invocation

<xsl:apply-templates select="//name" /><xsl:apply-templates select="//name" /> yieldsyields ""aa,,bb,,cc,,dd" " ( (←← single node list); single node list);

With invocation fromWith invocation from <xsl:template match="namelist"><xsl:template match="namelist">

<xsl:apply-templates select="name" /><xsl:apply-templates select="name" />

we'd getwe'd get ""aa,,bb"" andand ""cc,,dd"" (Clever, and tricky!) (Clever, and tricky!)


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Conditional processing (2)Conditional processing (2)

A case construct (A case construct ( switchswitch in Java): in Java): <xsl:choose><xsl:choose>

instantiated: -->

<xsl:when test="<xsl:when test="ExprExpr11">"> … … </xsl:when></xsl:when>

<xsl:when test="<xsl:when test="ExprExpr22">"> … … </xsl:when></xsl:when>… …

' is instantiated: --><xsl:otherwise><xsl:otherwise> … … </xsl:otherwise></xsl:otherwise>

</xsl:choose></xsl:choose>


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Example (cont; Eliminating duplicate names)Example (cont; Eliminating duplicate names)

Only the Only the current()current() node accessible in current node list node accessible in current node list– but can refer to nodes in the source treebut can refer to nodes in the source tree– Process just the first one of duplicate Process just the first one of duplicate namenames: s: <xsl:for-each select="//name"><xsl:for-each select="//name"> <xsl:sort select="last"/><xsl:sort select="last"/><xsl:sort select="first" /> <xsl:sort select="first" /> <xsl:if test="not(<xsl:if test="not(

preceding::name[first=current()/first preceding::name[first=current()/first and and

last=current()/last] )">last=current()/last] )"> <LI><xsl:value-of select="last" <LI><xsl:value-of select="last" />, <xsl:value-of select="first"/></LI> />, <xsl:value-of select="first"/></LI></xsl:if></xsl:if>

</xsl:for-each></xsl:for-each>


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Numbering Document ContentsNumbering Document Contents

Formatted numbers can be inserted in the result Formatted numbers can be inserted in the result tree by element tree by element <<xsl:number xsl:number />/> – by the position of the current node in the source treeby the position of the current node in the source tree– nodes to be counted specified by a nodes to be counted specified by a countcount pattern pattern– supports common numbering schemes : single-level, supports common numbering schemes : single-level,

hierarchical, and sequential through levelshierarchical, and sequential through levels

Typical cases in following examplesTypical cases in following examples» (Complete specification rather complex)(Complete specification rather complex)

Example 1: Numbering list itemsExample 1: Numbering list items


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Generating numbers: Example 1Generating numbers: Example 1

<xsl:template match="ol/item"><xsl:template match="ol/item">  (items) --> <xsl:number format="1. "/><xsl:number format="1. "/> <xsl:apply-templates/> <xsl:apply-templates/><xsl:template><xsl:template>

itemitem itemitem itemitem

olol

apricotapricot bananabanana coconutcoconut

1.1. 2.2. 3.3.

apricotapricotbananabananacoconutcoconut


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Hierarchical numbering (1, 1.1, 1.1.1, 1.1.2, …) Hierarchical numbering (1, 1.1, 1.1.1, 1.1.2, …) for titles of chapters, titles of their sections, and for titles of chapters, titles of their sections, and titles of subsections:titles of subsections:<xsl:template match="title"><xsl:template match="title"> <xsl:number level="multiple"<xsl:number level="multiple" count="chap | sect | subsect" count="chap | sect | subsect" format="1.1 "/> format="1.1 "/> <xsl:apply-templates/> <xsl:apply-templates/></xsl:template></xsl:template>


24


11 1.11.1 1.1.11.1.1 22

chapchap

SweetsSweets

titletitle

titletitle

BerriesBerries

sectsect

subsectsubsect

CherryCherry

titletitle

chapchap

titletitle

VegetablesVegetables

. . .. . .

. . .. . .

SweetsSweets BerriesBerries CherryCherry VegetablesVegetables


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Example 2: VariationExample 2: Variation

As above, but number titles within appendices As above, but number titles within appendices with A, A.1, A.1.1, B.1 etc:with A, A.1, A.1.1, B.1 etc:

<xsl:template match="appendix//title"><xsl:template match="appendix//title"> <xsl:number level="multiple" <xsl:number level="multiple" count="appendix | sect | subsect" count="appendix | sect | subsect" format="A.1 "/> format="A.1 "/> <xsl:apply-templates/> <xsl:apply-templates/></xsl:template></xsl:template>


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Example 2: VariationExample 2: Variation

AA A.1A.1 A.1.1A.1.1 BB

appendixappendix

SweetsSweets

titletitle

titletitle

BerriesBerries

sectsect

subsectsubsect

CherryCherry

titletitle

titletitle

VegetablesVegetables

. . .. . .

. . .. . .

SweetsSweets BerriesBerries CherryCherry VegetablesVegetables

appendixappendix


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Sequential numbering of notesSequential numbering of notes withinwithin chapterschapters::(more precisely: starting anew at the start of any chapter)(more precisely: starting anew at the start of any chapter)

<xsl:template match="note"><xsl:template match="note"> <xsl:number level="any" <xsl:number level="any" from="chap" from="chap" format="(1) "/> format="(1) "/> <xsl:apply-templates/> <xsl:apply-templates/></xsl:template></xsl:template>


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Ex 3: Sequential numbering Ex 3: Sequential numbering fromfrom chap chap

chapchap

Yes!Yes!

notenote

notenote

No!No!

sectsectPerhaps?Perhaps?

notenotenotenote

OKOK

. . .. . .

. . .. . .(1)(1) (2)(2) (3)(3) (1)(1)

Yes!Yes! No!No! Perhaps?Perhaps? OKOK

chapchap


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5.2 Computing with XSLT5.2 Computing with XSLT

XSLT is a declarative rule-based languageXSLT is a declarative rule-based language– for XML transformationsfor XML transformations– Could we use it for general computing?Could we use it for general computing?– What is the exact computational power of XSLT?What is the exact computational power of XSLT?

We've seen some programming-like features:We've seen some programming-like features:– iteration over source nodes (iteration over source nodes (xsl:xsl:for-eachfor-each))

» in XSLT 2.0 iteration over arbitrary sequencesin XSLT 2.0 iteration over arbitrary sequences

– conditional evaluation (conditional evaluation (xsl:xsl:ifif andand xsl: xsl:choosechoose))


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Computing with XSLTComputing with XSLT

Further programming-like features:Further programming-like features:– variablesvariables (names bound to (names bound to non-updatablenon-updatable values): values): <xsl:for-each select="//name"><xsl:for-each select="//name"> <xsl:variable name="LAndF" <xsl:variable name="LAndF"

select="concat(last, ', ', first)"select="concat(last, ', ', first)" />/> ......

... ...</xsl:for-each></xsl:for-each>

– callablecallable named templatesnamed templates withwith parametersparameters:: <xsl:call-template name="process-name"><xsl:call-template name="process-name">

<xsl:with-param name="pname" select="$LAndF" /> <xsl:with-param name="pname" select="$LAndF" /> </xsl:call-template> </xsl:call-template>


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Result Tree FragmentsResult Tree Fragments

Result tree fragmentsResult tree fragments built by templates can be stored, too: built by templates can be stored, too:

<xsl:variable name="fooBar"><xsl:variable name="fooBar"><FOO>BAR</FOO><FOO>BAR</FOO>

</xsl:variable></xsl:variable> They can only be used as string valuesThey can only be used as string values

substring($fooBar, 2, 2) = "AR"substring($fooBar, 2, 2) = "AR" or inserted in the result:or inserted in the result:

<xsl:copy-of select="$fooBar" /><xsl:copy-of select="$fooBar" />

(XSLT 2.0 allows unlimited processing of (computed) (XSLT 2.0 allows unlimited processing of (computed) sequences)sequences)


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Visibility of Variable BindingsVisibility of Variable Bindings

The binding is The binding is visiblevisible in following siblings of in following siblings of xsl:variable,xsl:variable, and in their descendants:and in their descendants:

<xsl:for-each select="//name"><xsl:for-each select="//name"> <xsl:variable name="LAndF" <xsl:variable name="LAndF"

select="concat(last, ', ', first)"select="concat(last, ', ', first)" />/> ... ... <xsl:call-template name="process-name"> <xsl:call-template name="process-name">

<xsl:with-param name="pname" <xsl:with-param name="pname" select="$LAndF" />select="$LAndF" /> </xsl:call-template> </xsl:call-template>

... ...

</xsl:for-each></xsl:for-each><TABLE> . . . </TABLE><TABLE> . . . </TABLE>


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A Real-Life ExampleA Real-Life Example

We used LaTeX to format an XML article. For this, we We used LaTeX to format an XML article. For this, we needed to map source table structuresneeded to map source table structures

<tgroup cols="3"><tgroup cols="3">......

</tgroup> </tgroup>to corresponding LaTeX environments:to corresponding LaTeX environments:

\begin{tabular}{lll} %3 left-justified \begin{tabular}{lll} %3 left-justified colscols

... ... \end{tabular}\end{tabular}

How to do this? How to do this?


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Possible solution (for up to 4 columns)Possible solution (for up to 4 columns)

<xsl:template match="tgroup"><xsl:template match="tgroup">

\begin{tabular}{l\begin{tabular}{l

} }<xsl:apply-templates /><xsl:apply-templates />

\end{tabular}\end{tabular}

</xsl:template></xsl:template>

OK, but inelegant!OK, but inelegant! How to support arbitrarily many columns?How to support arbitrarily many columns?

<xsl:if test="@cols > 1">l</xsl:if<xsl:if test="@cols > 1">l</xsl:if ><xsl:if test="@cols > 2">l</xsl:if><xsl:if test="@cols > 2">l</xsl:if ><xsl:if test="@cols > 3">l</xsl:if>><xsl:if test="@cols > 3">l</xsl:if>


35

More General Solution (1/2)More General Solution (1/2)

Pass the column-count to a named template which Pass the column-count to a named template which generates the requested number of ‘generates the requested number of ‘ll’s:’s:

<xsl:template match="tgroup"><xsl:template match="tgroup">

\begin{tabular}{\begin{tabular}{

} } <xsl:apply-templates /><xsl:apply-templates />

\end{tabular}\end{tabular}


<xsl:call-template name="gen-cols"><xsl:call-template name="gen-cols"> <xsl:with-param name="count" select="<xsl:with-param name="count" select="@cols@cols" />" /> <xsl:with-param name="symb" select="'l'" /><xsl:with-param name="symb" select="'l'" /> </xsl:call-template></xsl:call-template>


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Solution 2/2: Recursive Solution 2/2: Recursive gen-colsgen-cols

<xsl:template name="gen-cols"><xsl:template name="gen-cols">

<xsl:param name="count" /><xsl:param name="count" />

<xsl:param name="symb" /><xsl:param name="symb" />

<xsl:if test="$count > 0"><xsl:if test="$count > 0"><xsl:value-of select="$symb" /><xsl:value-of select="$symb" /><xsl:call-template name="gen-cols"><xsl:call-template name="gen-cols">

<xsl:with-param name="count" <xsl:with-param name="count" select="$count - 1" />select="$count - 1" />

<xsl:with-param name="symbol" <xsl:with-param name="symbol" select="$symbol" />select="$symbol" />

</xsl:call-template></xsl:call-template>

</xsl:if></xsl:if>


formal parametersformal parameters


37

Stylesheet ParametersStylesheet Parameters

Stylesheet can get params from command line, or through Stylesheet can get params from command line, or through JAXP with JAXP with

Transformer.setParameter(name, value)Transformer.setParameter(name, value) ::<xsl:transform ... ><xsl:transform ... >

<xsl:output method="text" /><xsl:output method="text" />

<xsl:param name="In" select="0" /><xsl:param name="In" select="0" /> <xsl:template <xsl:template match="/">match="/">

<xsl:value-of select="2*<xsl:value-of select="2*$In$In"/> </xsl:template>"/> </xsl:template>

</xsl:transform></xsl:transform>

$ java -jar saxon.jar dummy.xml double.xslt In=120$ java -jar saxon.jar dummy.xml double.xslt In=120

240240

default valuedefault value


38

Computational power of XSLTComputational power of XSLT

XSLT seems quite powerful, but how powerful is it?XSLT seems quite powerful, but how powerful is it?– Implementations provide extension mechanisms, e.g., to Implementations provide extension mechanisms, e.g., to

call arbitrary Java methodscall arbitrary Java methods– Are there limits to XSLT processing that we can do Are there limits to XSLT processing that we can do

withoutwithout extensions? extensions?

AnyAny algorithm can be shown computable with plain algorithm can be shown computable with plain XSLTXSLT– by simulating Turing machines, by a recursive named by simulating Turing machines, by a recursive named

template with string parameters template with string parameters (see 2005 lecture notes, or References)(see 2005 lecture notes, or References)


39

What does this mean?What does this mean?

XSLT has XSLT has full algorithmic powerfull algorithmic power– (It is "Turing-complete")(It is "Turing-complete")– Is this intentional?Is this intentional?

» Awkward as a general-purpose programming language!Awkward as a general-purpose programming language!

– Impossible to recognise non-terminating Impossible to recognise non-terminating transformations automatically transformations automatically (( the "halting problem" has no algorithmic solution) the "halting problem" has no algorithmic solution)

» could attempt "denial-of-service" attacks with non-terminating could attempt "denial-of-service" attacks with non-terminating style sheets(!) style sheets(!)

Documents

SDPL 2007XSLT: Additional Features and Computing1 5.1 Additional Features n XPath for arithmetics, cross-references, and string manipulation n Generating