Subject: RE: [xsl] Copy-per-default From: Fredrik Bengtsson <Fredrik.Bengtsson@xxxxxxxxxxxx> Date: Thu, 21 Apr 2011 08:11:15 +0000 |
(sorry, fat fingers) ... it would make the transform larger. So for this particular application I will stick to the whitelisting approach where I clearly state exactly every step that I expect to happen along the way, and nothing else. Then again, I am not very experienced in these matters and as my understanding matures I'll probably try to reevaluate this. Thanks for your help! /F -----Original Message----- From: Fredrik Bengtsson Sent: den 21 april 2011 10:09 To: 'xsl-list@xxxxxxxxxxxxxxxxxxxxxx' Subject: RE: [xsl] Copy-per-default Yeah, things work great now, albeit with a caveat or two (see my e-mail to Florent Georges). I understand the point you are making regarding the *|/ template. It has its benefits, but I am sort of a control freak or perfectionist if you will. For my part, I'd really prefer "whitelisting" the things I want to happen and being meticulous in the pattern design. Someone suggested adding a "null" template for d:book/d:info specifically instead of for *, but that'd be a form of blacklisting and relies on me knowing any and all possible subnode types today and for all time to come. Not only could that lead to unforeseen consequences (text garbage in the fo), it would make the0020 -----Original Message----- From: Brandon Ibach [mailto:brandon.ibach@xxxxxxxxxxxxxxxxxxx] Sent: den 21 april 2011 01:38 To: xsl-list Subject: Re: [xsl] Copy-per-default 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.Bengtsson@xxxxxxxxxxxx> 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.ibach@xxxxxxxxxxxxxxxxxxx] > 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.Bengtsson@xxxxxxxxxxxx> 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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