Re: [xsl] How to test with XPath the existence of a certain branch of a <choice> statement?

[Abel Braaksma <abel.online@xxxxxxxxx>]

Hi Ben,

Normally, when doing XSLT transformations, you'd let the processor 
decide for you. If you, for instance, do the following:

   <xsl:apply-templates select="parent/choice/sequence" />

it will process all sequences which can be "caught" (handled) by your 
templates:

   <xsl:template match="sequence">
     ...
   </

Now, in the above situation, you can test for the presence of children 
in several ways. Suppose you want to do something special with empty 
<sequence> nodes and something with filled <sequence> nodes. Then you 
can solve that as follows:

   <!-- catches all filled sequence nodes -->
   <xsl:template match="sequence[*]">
     <xsl:text>found a filled sequence!</xsl:text>
   </

   <!-- catches the rest, i.e., empty nodes (or nodes with only text) -->
   <xsl:template match="sequence">
     <xsl:text>found an empty one!</xsl:text>
   </

The same test you can also apply in an xsl:if:

   <!-- contains at least an element -->
   <xsl:if test="sequence[*]">....</

   <!-- contains element <aaaa> -->
   <xsl:if test="sequence[aaaa]">....</

   <!-- contains any node, even a text node or comment node -->
   <xsl:if test="sequence[node()]">....</

   <!-- any sequence -->
   <xsl:if test="sequence">....</

Here you immediately see the problem with xsl:if, if you have to adjust 
for all case, you need to inverse your logic. In this case, testing for 
emptiness can be done as follows

   <!-- empty sequence element -->
   <xsl:if test="sequence[not(*)]">....</


Kind regards,

Abel Braaksma


Ben Stover wrote:
> For an XSLT script I need to check wether one certain branch of a <choice> statement is present.
> The critical part of the XML statement look like as follows (<choice> and <sequence> are taken/inserted from the 
> underlying XSD schema file):
>
> <parent>
>   <choice>
>      <sequence>
>         <aaa>...</aaa>
>         <bbb>...</bbb>
>     </sequence>
>       <sequence>
>         <aaa>...</aaa>
>         <ccc>...</ccc>
>     </sequence>
>      <sequence>
>         .....
>     </sequence>
>   </choice>
> </parent>
>
> As you can see a XML doc can contain one of the three sequence branches.
>
> How do I check with XPath if the first branch is currently filled in an XML doc?
>
> If I code e.g.
>
>   test=.../parent/aaa
>
> then it is not clear if the first or second branch is present.
>
> Can anyone give me a hint?
>
> Thank you
> Ben