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Re: [xsl] Copy-per-default

2011-04-20 18:37:46
I think, over time, you'll find it's actually quite intuitive.

Just to clarify the defaults, the values of attributes are output, but
only if you explicitly apply templates to the attributes, as the
default for elements (and the root node) is to apply templates (in the
current mode, if any) to just the child nodes, and attributes are not
children.

So, you could create the empty template with match="*" (no need for
@*, as noted above), but I think you'll find in most cases that this
short-circuits much of the power and elegance of XSLT.  Of course,
it's hard for me to say what's right in your case, but it seems likely
that you'll be better off with more selective empty templates, such as
one with match="book/info", if you want to suppress that whole
hierarchy.  That single template will cover the whole thing, since
elements further down will never have templates applied to them.

-Brandon :)


On Wed, Apr 20, 2011 at 6:48 PM, Fredrik Bengtsson
<Fredrik(_dot_)Bengtsson(_at_)lemontree(_dot_)se> wrote:
Wow, now come to think of it I DID stop to think at one time why I did not 
have to write a specific rule for text(). This explains it. Well that 
behavior is fine, I'll keep that. But getting the values of @* and recursing 
into *|/ are a downright disaster in my case!

What I need to express is that whenever a node is examined that does not have 
an explicit matching template (well, except the one template that achieves 
just that, of course), then that node is discarded entirely and is NOT 
descended into, i.e. its children are ignored too. So ... if I understand 
this correctly, I should be able to get what I want just by adding

<xsl:template match="*|@*" />

I'll try that at work tomorrow.

As an aside - wow, that combination of rules you listed below sure do give 
strange results sometimes. <book> has an entire <info> hierarchy below it, 
and all of its textual content is copied into the output in one big mess, but 
with all of the actual elements stripped out. That's just ... Well, now it 
makes sense anyway, thanks for informing me.

/F

-----Original Message-----
From: Brandon Ibach 
[mailto:brandon(_dot_)ibach(_at_)single-sourcing(_dot_)com]
Sent: den 20 april 2011 17:59
To: xsl-list
Subject: Re: [xsl] Copy-per-default

Most (probably all, though I think we'd need more details on the latter 
issue) of the behavior you're seeing can be explained by XSLT's built-in 
templates.  See section 5.8 of the XSLT 1.0 specification [1], but in short, 
they are:

<xsl:template match="*|/">
 <xsl:apply-templates/>
</xsl:template>

<xsl:template match="*|/" mode="m"><!-- One of these for each mode -->
 <xsl:apply-templates mode="m"/>
</xsl:template>

<xsl:template match="text()|@*">
 <xsl:value-of select="."/>
</xsl:template>

<xsl:template match="processing-instruction()|comment()"/>

-Brandon :)

[1] http://www.w3.org/TR/1999/REC-xslt-19991116#built-in-rule

On Wed, Apr 20, 2011 at 11:24 AM, Fredrik Bengtsson 
<Fredrik(_dot_)Bengtsson(_at_)lemontree(_dot_)se> wrote:
Hi,

I am using FOP trunk to generate PDFs from DocBook documents on the command 
line. Fop.bat is doing the XSL transformation, using whatever engine fop 
uses (xalan?). I have written the XSLT entirely by myself, i.e. I am not 
using any default DocBook transform or similar. The transform is small and 
under my strict control.

I am having the problem that the transform does not behave as expected in 
two ways:
* Contents of nodes are being copied to the output as if there were
some kind of identity transform in effect by default even though I
have not written one, and
* Matches far down in the document cannot fetch data that existed
earlier in the document, as if select="/x" selected the x
post-transform instead of pre-transform


Imagine a document like this (ignoring namespaces etc for brevity):

<book>
 <titleabbrev>THEDOC</titleabbrev>
 <chapter>
   <title>Ch. 2: The chapter</title>
   <titleabbrev>Ch. 2</titleabbrev>
 </chapter>
</book>


If I have the following transforms in place:

<xsl:template match="/d:book">
 <!-- ignoring root, page-sequence etc for brevity -->
 <xsl:apply-templates />
</xsl:template>

<xsl:template match="d:chapter">
 <xsl:apply-templates />
</xsl:template>

<xsl:template match="d:chapter/d:title">
 <fo:block> ... ... </fo:block>
</xsl:template>


Then for some reason the titleabbrev appears in the output even though I 
have not made any rule explicitly matching it. It is caught along with the 
title inside the apply-templates under d:chapter. I thought that this would 
not happen, unless I really added a matching template of some sort, for 
example an identity transform.


I then just for fun tried to add the following template:

<xsl:template match="*" />


That got rid of the offending titleabbrev, BUT it also had the effect of 
breaking another template that special-cases the first chapter:

<xsl:template match="d:chapter[1]">
 <xsl:variable name="abbr">
   <xsl:value-of select="/d:book/d:titleabbrev" />
 </xsl:variable>
 <!-- note: that selects a node that is higher up in the document -->
 <!-- now do something with $abbr -->
</xsl:template>


It seems that at that point, book/titleabbrev has already been transformed, 
i.e. removed due to the catch-all template above, so $abbr is empty. That 
strikes me as extremely strange; should the select not grab nodes from the 
original unmodified document? If I remove the catch-all, $abbr is set 
properly just as expected.

This is really confusing! And again - I am not using a huge third-party 
transform and modifying it, but rather using a really small, custom-written 
and strict one under my control.

/Fredrik


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