Wow -- that's appealingly simple. What I actually want is the following:



- CONTEXT: call: (3 tasks)
   - Task: Make a phone call
   - Task: This is to be done at home, and is a phone call
   - Task: This is a call to be made from work
- CONTEXT: home: (2 tasks)
   - Task: This is to be done at home
   - Task: This is to be done at home, and is a phone call
- CONTEXT: work: (1 tasks)
   - Task: This is a call to be made from work

I think that's what you had in mind, but the last context label should be "work", not "work call". I'm using libxslt tho so I don't think the XSLT 2.0 solution will work for me yet.



Ramon



Andrew Welch wrote:



I'm trying to group and sort a list of tasks by category, where one 
<task> may have multiple categories identified by <context> 
tags. I find 
that I get different results depending on the ordering in the 
source XML:



<tasks>

   <task>

       <subject>This is to be done at home</subject>

       <context>home</context>

   </task>

   <task>

       <subject>No context so skip this one.</subject>

   </task>

   <task>

       <subject>Make a phone call</subject>

       <context>call</context>

   </task>

   <task>

       <subject>This is to be done at home, and is a phone 
call</subject>

       <context>home</context>

       <context>call</context>

   </task>

   <task>

       <subject>This is a call to be made from work</subject>

       <context>work</context>

       <context>call</context>

   </task>

</tasks>



Using the following XSLT, I get what I want:



<xsl:stylesheet version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

   <xsl:output method="xml" version="1.0" encoding="UTF-8" 
indent="yes"/>

   <xsl:key name="tasks-by-context" match="task" use="context"/>

   <xsl:template match="/">

       <ul>

           <xsl:for-each select="//task[count(. | 
key('tasks-by-context', context)[1]) = 1][count(context)>0]">

               <xsl:sort select="subject"/>

               <xsl:variable name="c" select="context"/>

               <li>

                   CONTEXT: <xsl:value-of select="$c"/>: 
(<xsl:value-of 
select="count(key('tasks-by-context',$c))"/> tasks)

                   </li>

               <ul>

                   <xsl:for-each 
select="key('tasks-by-context', $c)">

                           <li>

                                   Task : <xsl:value-of 
select="subject"/>

                           </li>

                   </xsl:for-each>

               </ul>

           </xsl:for-each>

       </ul>

   </xsl:template>

</xsl:stylesheet>



As I'm skipping uncategorized tasks (i.e. with no <context> 
children), I 
get the following output:



- CONTEXT: call: (3 tasks)
   - Task : Make a phone call
   - Task : This is to be done at home, and is a phone call
   - Task : This is a call to be made from work
- CONTEXT: home: (2 tasks)
   - Task : This is to be done at home
   - Task : This is to be done at home, and is a phone call

However, this behavior differs if the original <task> 
elements are in a 
different order. For example, moving the "Make a phone call" 
task to the 
end of the <tasks> list reduces the output to the following:



- CONTEXT: home: (2 tasks)
   - Task : This is to be done at home
   - Task : This is to be done at home, and is a phone call

So it looks like my key definition is no longer picking up 
"call" as a 
valid key item. I'm actually not sure whether I'm using the <xsl:key> 
tag correctly here -- will it match and index a single <task> node 
multiple times if it contains multiple tags?

   








Here's an XSLT 2.0 solution, although I'm not sure your desired output
is correct:

<xsl:template match="/">
   <xsl:for-each-group select="/tasks/task" group-by="context">
       <xsl:text>- CONTEXT: </xsl:text>
       <xsl:value-of select="context"/>: (<xsl:text/>
       <xsl:value-of select="count(current-group())"/>
tasks)&#xa;<xsl:text/>
       <xsl:for-each select="current-group()/subject">
           <xsl:text>    - Task: </xsl:text>
           <xsl:value-of select="."/><xsl:text>&#xa;</xsl:text>
       </xsl:for-each>
   </xsl:for-each-group>
</xsl:template>

This will produce:



- CONTEXT: call: (3 tasks)
   - Task: Make a phone call
   - Task: This is to be done at home, and is a phone call
   - Task: This is a call to be made from work
- CONTEXT: home: (2 tasks)
   - Task: This is to be done at home
   - Task: This is to be done at home, and is a phone call
- CONTEXT: work call: (1 tasks)
   - Task: This is a call to be made from work

Whereas your desired output is:



- CONTEXT: call: (3 tasks)
   - Task : Make a phone call
   - Task : This is to be done at home, and is a phone call
   - Task : This is a call to be made from work
- CONTEXT: home: (2 tasks)
   - Task : This is to be done at home
   - Task : This is to be done at home, and is a phone call

Wouldn't you want to output the 'work' context as well?



cheers
andrew