XPath 2.0 quantified expressions. Implementation with XSLT 1.0

XPath 2.0 language has introduced new syntax and semantics as compared to XPath 1.0 language, for e.g like the XPath 2.0 quantified expressions.

Following is an XPath 2.0 grammar, for the quantified expressions (quoted from the XPath 2.0 language specification),

QuantifiedExpr    ::=    ("some" | "every") "$" VarName "in" ExprSingle ("," "$" VarName "in" ExprSingle)* "satisfies" ExprSingle

The XPath 2.0 quantified expression, when evaluated over a list of XPath data model items, returns either boolean 'true' or a 'false' value.

I'm able to, suggest an XSLT 1.0 code pattern (tested with Apache XalanJ), that can implement the logic of XPath 2.0 like quantified expressions. Following is an example, illustrating these concepts,

XML input document:

<?xml version="1.0" encoding="UTF-8"?>

<elem>

  <a>5</a>

  <a>5</a>

  <a>4</a>

  <a>7</a>

  <a>5</a>

  <a>5</a>

  <a>7</a>

  <a>5</a>

</elem> 

XSLT 1.0 stylesheet, implementing the XPath 2.0 "every" like quantified expression (i.e, universal quantification):

<?xml version="1.0"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

                         xmlns:exslt="http://exslt.org/common"

                         exclude-result-prefixes="exslt"

                         version="1.0">

   <xsl:output method="text"/>

   <xsl:template match="/elem">

      <xsl:variable name="temp">

         <xsl:for-each select="a">           

            <xsl:if test="number(.) &gt; 3">

              <yes/>

            </xsl:if>

         </xsl:for-each>

      </xsl:variable>

      <xsl:value-of select="count(exslt:node-set($temp)/yes) = count(a)"/>

   </xsl:template>

</xsl:stylesheet>

The above XSLT stylehseet, produces a boolean 'true' result, if all XML "a" input elements have value greater than 3, otherwise a boolean 'false' result is produced.

XSLT 1.0 stylesheet, implementing the XPath 2.0 "some" like quantified expression (i.e, existential quantification):

<?xml version="1.0"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

                         xmlns:exslt="http://exslt.org/common"

                         exclude-result-prefixes="exslt"

                         version="1.0">

   <xsl:output method="text"/>

   <xsl:template match="/elem">

      <xsl:variable name="temp">

         <xsl:for-each select="a">           

            <xsl:if test="number(.) = 4">

              <yes/>

            </xsl:if>

         </xsl:for-each>

      </xsl:variable>

      <xsl:value-of select="count(exslt:node-set($temp)/yes) &gt;= 1"/>

   </xsl:template>

</xsl:stylesheet>

The above XSLT stylehseet, produces a boolean 'true' result, if at-least one XML "a" input element has value equal to 4, otherwise a boolean 'false' result is produced.

Within the above cited XSLT 1.0 stylesheets, we've used XSLT "node-set" extension function (that helps to convert an XSLT 1.0 "result tree fragment" into a node set).

We can therefore conclude that, within an XSLT 1.0 environment, we can largely simulate logic of many XPath 2.0 language constructs.