Re: Nested/embedded/self-referential path expressions.

Jeni Tennison wrote:
> 
> Hi Ed,
> 
> > What I want to do is combine the if with the "match=..." clause of
> > the template. The problem is that I need to reference the "name()"
> > of the context/element with the "name()" in a different
> > context/element. The logical expression would be somethink like the
> > following:
> >
> > <xsl:template match="Row/*[/Table/Columns/*[{inner context name}={outer
> > context name}]]">
> >
> > Can/how do I reference a element/component of the outer context for
> > comparison in the inner context?
> 
> You can't. One method you can use in this situation, though, is to
> define a key that can get you from a name to a column (child of the
> Columns element):
> 
> <xsl:key name="columns" match="/Table/Columns/*" use="name()" />
> 
> Then you can do:
> 
> <xsl:template match="Row/*[key('columns', name())]">
>   ...
> </xsl:template>
> 
> In general it's a bad idea to use complicated conditions like this
> within patterns; you'd probably be better off having a general
> template for all elements within Row elements, but only applying
> templates to those that share a name with a column:
> 
> <xsl:template match="Row">
>   <xsl:apply-templates select="*[key('columns', name())]" />
> </xsl:template>
> 
> <xsl:template match="Row/*">
>   ...
> </xsl:template>

Seems as though the pattern in the "select" is darn near as complex as
the match: "*[key('columns', name())]" versus "Row/*[key('columns',
name())]".  Did we actually gain much ground here? Are there underlying
reasons why complexity in the "select" is preferred over the "match"?

What I decided to do (although I may change given your feedback) is two
templates and modes: one template to filter the columns, other templates
to process the filtered nodes:

<xsl:templateatch="gnsl:Row/*">
   <xsl:variable name="MyName" select="name()" />
   <xsl:if test="$TableColumns[name()=$MyName]" >
      <xsl:apply-templates select="." mode="ColumnContent" />
   </xsl:if>
</xsl:template>

<xsl:template  mode="ColumnContent" match="gnsl:Row/*>
....
</xsl:template>

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