xml-dev - Re: How to "query" into a different xml?

["Thomas B. Passin" <tpassin@home.com>]

José Manuel Beas asks a significant question about xslt
(reproduced after this response) -

So as as I know, there are two ways to do this.

1)  Use the Saxon xslt processor so you can use its
"evaluate()" extension function to evaluate your path
statement as a node set specification (see Michael Kay's
book "XSLT Programmer's Reference", p 649).  Or,

2) Write a stylesheet to create a stylesheet that does what
you want, then run the second stylesheet.

I think that xslt SHOULD add an evaluate function, and right
away, too!

Here's a working ( I tried it and got the result you say you
want) version of your styleshseet, using the Saxon
"evaluate()" approach:

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:saxon="http://icl.com/saxon">
<!--====== Note the saxon namespace! =========-->

<!--====== This part is unchanged ========-->
<xsl:template match="part">
  <H1><xsl:value-of select="@name"/></H1>
  <xsl:variable name="OBJECTNAME" select="class"/>
  <xsl:variable name="QUERYSTRING" select="query"/>
  <xsl:variable name="FILENAME"
select="document('master.xml')//object[@name =
$OBJECTNAME]/@href"/>
  objectname = <xsl:value-of select="$OBJECTNAME"/><BR/>
  filename = <xsl:value-of select="$FILENAME"/><BR/>
  query = <xsl:value-of select="$QUERYSTRING"/><BR/>
<!--===============================-->

<!--==== use for-each to set the current node to the foreign
document ===-->
 <xsl:for-each select="document($FILENAME)">

<!--==== Build the query string and evaluate it ======-->
 <xsl:variable name="path"
select="saxon:evaluate(concat('//',$QUERYSTRING))"/>
  <PRE>

<!--=== The evaluated path contains your data =====-->
  <xsl:value-of select="$path"/>
  </PRE>
  </xsl:for-each>
</xsl:template>
</xsl:stylesheet>

Enjoy!

Tom Passin

>
> We have an xml file with a catalogue of parts, but their
descriptions
> are kept in a different xml file (this file depends on the
class of
> the part).
>
> These is the file:
>
> "parts.xml"
> ------------
> <parts>
>   <part name="BigSquare">
>     <class>square</class>
>     <query>square[@id = '001']/color</query>
>   </part>
>   <part name="SmallCylinder">
>     <class>cylinder</class>
>     <query>cylinder[@id = '001']/color</query>
>   </part>
> </parts>
> -----------
>
> I am transforming it into HTML with an XSLT by matching
the "part"
> template.
>
> "process.xslt"
> -----------
> <xsl:template match="part">
>   <H1><xsl:value-of select="@name"/></H1>
>   <xsl:variable name="OBJECTNAME" select="class"/>
>   <xsl:variable name="QUERYSTRING" select="query"/>
>   <xsl:variable name="FILENAME"
select="document('master.xml')//object
> [@name = $OBJECTNAME]/@href"/>
>   objectname = <xsl:value-of select="$OBJECTNAME"/><BR/>
>   filename = <xsl:value-of select="$FILENAME"/><BR/>
>   query = <xsl:value-of select="$QUERYSTRING"/><BR/>
>   <PRE>
>   <xsl:value-of
select="document($FILENAME)//$QUERYSTRING"/>
>   </PRE>
> </xsl:template>
> -----------
>
> What I am doing is to look for the filename corresponding
to each
> part "class" (into "master.xml") and then apply the
"query" to that
> xml file.
>
> But it doesn't work. I get the following error:
>
> oracle.xml.parser.v2.XSLException: XSL-1013: Error in
> expression: 'document($FILENAME)//$QUERYSTRING'.
>
>
> The rest of the files used are:
>
> "master.xml"
> ------------
> <master>
>   <objects>
>     <object name="square" href="squares.xml"/>
>     <object name="cylinder" href="cylinders.xml"/>
>   </objects>
> </master>
> ------------
> "squares.xml"
> ------------
> <squares>
>   <square id="001">
>     <color>Black</color>
>     <size>big</size>
>   </square>
>   <square id="002">
>     <color>Blue</color>
>     <size>small</size>
>   </square>
> </squares>
> -----------
>
> It's curious, but when I replace
>   <xsl:value-of
select="document($FILENAME)//$QUERYSTRING"/>
> by (for example)
>   <xsl:value-of select="document($FILENAME)//square[@id
> = '001']/color"/>
> I get the following:
> -----
> <PRE>
>   Black
> </PRE>
> -----
>
> Which is EXACTLY what I am trying to obtain.
>
> Any ideas???
>