RE: [xsl] Built in templates and issues getting the XSLT processor to navigate an input document

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

At 06:25 AM 9/25/2007, Mike Kay wrote:
> <xsl:template match="a/b">
>   <xsl:message> b found </xsl:message>
>     <xsl:apply-templates select="a/b/c"/>
>
> Your b element does not have a child called a, so select="a/b/c" starting at
> b will select nothing. You want select="c".

This is because "a/b/c" is a relative path expression, which starts 
at the context node, which here is the current node (the node 
matching the template, which would be each 'b' element as it is matched).

"a/b/c" could also be written "child::a/child::b/child::c" (the long 
syntax), which has the virtue of making very clear what is happening, 
while of course being more verbose.

In contrast to a relative path, an absolute path such as "/a/b/c" 
would not navigate from the current node, but from the root of the 
document. But of course this would retrieve all 'c' elements inside 
'b' elements inside 'a' element children of the root (document node), 
not just 'c' elements inside the particular 'b' element you happen to 
be matching.

The notion of processing context, and (along with it) node selection 
using relative paths, is closely entangled with the processing 
model's notion of template matching, and a great part of what enables 
it to work so nicely.

Indeed, <xsl:apply-templates/> (in the built-in templates and 
elsewhere) is short for

<xsl:apply-templates select="child::node()"/>

... i.e., selecting all the child nodes of the node (element) 
matched, using a relative path.

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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