RE: Prevent compilation error for xsl:namespace in XSL

>   The goal is to write a named template that generates a 
> namespace node that can be copied to the result tree, using 
> either xsl:namespace, exslt:node-set(), *:node-set() or in 
> the worst case a dummy attribute whose the URI part of the 
> name is the namespace URI:
> 
>     IF available xsl:namespace
>       ...
>     ELSIF available exslt:node-set()
>       ...
>     # once for each other implementation specific node-set
>     # functions
>     ELSIF available *:node-set()
>       ...
>     ELSE
>       <xsl:attribute
>           name="{ concat(@prefix, ':dummy-for-xmlns') }"
>           namespace="{ @uri }"/>
> 
>   So what can I use in the first branch in the above algorithm?
> 
You should be able to do

<xsl:when test="element-available('xsl:namespace')">
  <xsl:namespace... version="2.0"/>
</xsl:when>

Under the XSLT 1.0 rules for forwards-compatible mode:

if it is an element in a template and XSLT 1.0 does not allow such elements
to occur in templates, then if the element is not instantiated, an error
must not be signaled...

However, it's known that XSLT 1.0 processors are not universally reliable in
their support for forwards-compatible mode, so you may need to do some
experiments to be sure this works.

Michael Kay
http://www.saxonica.com/