XPATH for IDREFS in XSL?

[Tristan Taylor]

Could anyone please explain to me how to create an XPATH expression to retrieve data that relates to a specific ID within an IDREFS string.
I would like to retrieve the data within the 'description' tags for each 'event' whose id's are referenced in the '@events' within the 'requirement' element.

Could anyone please explain this using the below information?
Thanks,
Tristan

DTD:
<!ELEMENT requirement (#PCDATA)>
<!ATTLIST requirement number ID #REQUIRED
events IDREFS #REQUIRED>
XML:
<requirement id="req1" events="ev1 ev2">All solutions to existing problems must be authorized by the technical director</requirement>
<event id="ev1">
<description>creating a solution</description>
</event>
<event id="ev2">
<description>implementing solution</description>
</event>

[Anonymous]

Hi Tristan,
First you need to update your DTD to specify that the id attribute of an event is of type ID. Then you can use the id() function as specified by XPATH.
For instance:
events.dtd

<!ELEMENT requirement (#PCDATA)>
<!ATTLIST requirement number ID #REQUIRED
events IDREFS #REQUIRED>
<!ATTLIST event id ID #REQUIRED>

events.xml

<?xml version="1.0"?>
<!DOCTYPE event SYSTEM "events.dtd">
<events>
<requirement id="req1" events="ev1 ev2">All solutions to existing problems must be authorized by the technical director</requirement>
<event id="ev1">
<description>creating a solution</description>
</event>
<event id="ev2">
<description>implementing solution</description>
</event>
<event id="ev3">
<description>making tea</description>
</event>
</events>

events.xsl

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/">
  <xsl:apply-templates select="//requirement"/>
</xsl:template>
<xsl:template match="requirement">
Requirement: <xsl:value-of select="."/>
Matching events:
<xsl:for-each select="id(@events)">
<xsl:text>- </xsl:text>
<xsl:value-of select="description"/>
<xsl:text>
</xsl:text>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>

will produce

Requirement: All solutions to existing problems must be authorized by the technical director
Matching events:
- creating a solution
- implementing solution

Hope this helps.
Cheers,
Beno�t
[This message has been edited by Beno�t d'Oncieu (edited September 04, 2001).]

[Tristan Taylor]

Thanks a Lot Beno�t,
You've made my life a lot easier.
Cheers,
Tristan