Re: [xsl] XSLT Dead?

["Andrew Welch" <andrew.j.welch@xxxxxxxxx>]

On 4/18/07, David Carlisle <davidc@xxxxxxxxx> wrote:
> > Well the answer I look for is that with xsl:apply-templates the
> > processing is controlled by the structure of the input document, while
> > with xsl:for-each the processing is controlled by the stylesheet.
>
> I think I'd fail the test:-)

It is looking like an unfair question...

> if I'm in an xhtml document and processing a p(aragraph) and do
> <xsl:template match="h:p">
>   <xsl:apply-templates select="/h:html/h:head/h:title"/>
>   <xsl:for-each select="node()">
>     <a id="generate-id()"/><xsl:copy-of select="."/>
>   </xsl:for-each>
> </xsl:template>
>
> Then I'd say that the first part is "pull" style where you have gone
> off and fetched data from elsewhere in the document, but it's coded with
> apply-templates, and the second part is "push" style where you are
> walking the children in document order, letting the input drive the
> result.
>
> so I think that the "pulliness" or "pushiness" of a stylesheet depends
> mostly on the nature of the xpaths used in select
> attributes. apply-templates select defaults to node() which is the
> canonical "push" example, and for-each has no default select so is
> often used for "pull" things. Also of course for-each is far more
> limited as it's equivaent to an apply template where every node is
> matched by the same template.

I've only ever considered push to be an empty <xsl:apply-templates/> -
as soon as you use a select it becomes pull.

Maybe this description is better: there are three trees in a line, the
leftmost tree is the input document, the middle tree is the stylesheet
and the right hand tree is the result document.    With push a _single
node_ is "pushed" across from the input document to the stylesheet,
where it is processed.  With pull a _selection_ of nodes is pulled
(built) by the stylesheet, and then processed.  Push can only be
invoked by <xsl:apply-templates/>, all others are pull.

So in your example above, I would consider both pull because the
stylesheet is driving the transform.

So maybe the one-liner definition is: "push processes the input one
node at a time in document order, pull processes a selection of node
from the input in a user defined order; push can only be invoked by
<xsl:apply-templates/>"...

...with a caveat that DC can make an xsl:for-each behave like an
<xsl:apply-templates/> :)