I have a fairly simple setup here (I've stripped out a few levels for clarity).

<Activity>
    <Item>Item Text
        <Answer>Answer Text</Answer>
    </Item>

    <Item>Item Text
    </Item>

    <Item ExampleItem="Yes">Item Text
        <Answer>Answer Text</Answer>
    </Item>
</Activity>

I'm outputting to another XML file. In determining whether to create certain tags in the output file, I need to do this in the Activity template:

IF the Activity has a descendant Item which itself has an Answer descendant, AND the Item's ExampleItem attribute does not equal Yes, THEN I generate an answer_key tag. As you can see from the sample, an Activity can have multiple Items - they will not all have Answer descendants, and in fact some Activities may not have any Items which have an Answer. Basically, I need to generate the tag only if there is at least one positive match for Item/whatever/Answer where Item/@ExampleItem <> "Yes".

I've never worked with "multiple levels" of ancestry, for lack of a better phrase - meaning testing for the existence of a specific descendent, then testing for the existence of a specific descendant of that. Is it possible this way, or do I need to do nested if statements?

<xsl:template match="//Activity">

    <xsl:if test="descendant::Item/descendant::Answer[@ExampleItem='Yes']">
    GETS AN ANSWER KEY
    </xsl:if>
</xsl:template>

You're almost there, you want

<xsl:if test="descendant::Item[@ExampleItem='Yes']/descendant::Answer">

It's surprising how often people forget that you can have predicates on any step in a path expression.

You could also write this as

<xsl:if test="descendant::Item[@ExampleItem='Yes'][descendant::Answer]">

or various other combinations for example

<xsl:if test="descendant::Item[descendant::Answer]/@ExampleItem = 'Yes'">

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

shorthand

   .//Item[@ExampleItem!='Yes']//Answer


or,

   descendant::Item[@ExampleItem!='Yes']/descendant::Answer

Regards
Bryan

Thank you both. I had actually gotten as far as

<xsl:if test="descendant::Item[descendant::Answer]">

after I posted, but couldn't figure out how to work in the attribute value. Things generally turn out to be a lot simpler than I'm trying to make them... :o)