Re: [xsl] Conditional text using attributes

[Michael Smith <smith at xml-doc dot org>]

Steve,

I think the inner workings of the DocBook stylesheets are such that
your example transform will perform as expected for conditionally
including some elements, but not for others -- for example:

  <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
    "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
  <article>
    <articleinfo>
      <title os="PC">Starting the timer using Microsoft Windows</title>
      <title os="Mac">Starting the timer using MacOS</title>
    </articleinfo>
    <para>Press the...</para>
  </article>

(I've included some expanded comments on that same example below,
after quoting parts of the previous messages for context.)

So instead of importing the DocBook templates, might it be possible
instead to write a straight XML to XML "conditional inclusion"
transform that will work with *any* well-formed XML document instance?

What I mean specifically is a transform that:

  * conditionally includes elements based simply on attribute
    names/values, without regard at all for the actual element names

  * is a "standalone" transform that doesn't rely on importing other
    stylesheets that contain templates matching the element names

Is that possible? How could it be expressed in XSLT?

I think there's a great need for this kind of capability in the
document-oriented XML world -- especially among documentation authors
who have come to rely on the conditional text features in FrameMaker.

   --Mike Smith


Comments on the DocBook case are after the following quoted sections.

Beth Fischi <bfischi@broadjump.com> writes:

> I'm trying to figure out how to exclude text and graphics from an
> output file (HTML or FO, for example) by testing for attributes in
> my XSL stylesheet. For instance, I have an XML file with
> instructions appropriate for both Macintosh users and Windows users.
>
> I'm using the DocBook DTD and Norm Walsh's DocBook XSL stylesheets

Steve Muench <Steve.Muench@oracle.com> writes:

> [...] Let's say your Docbook source looks like this:
> 
> <?xml version="1.0"?>
> <article>
>   <para>
>     Press the <emphasis os="PC">Left</emphasis> mouse button to start 
>     the timer. You can use the <emphasis os="Mac">Finder</emphasis>
>     <emphasis os="PC">Start Button</emphasis> to launch a new program.
>   </para>
> </article>
> 
> [...] we can create a "beth.xsl" stylesheet like the one below to
> import the base stylesheet, and add one or more templates that will
> take precedence over the templates from the imported stylesheet:
> 
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
>   <xsl:import href="norm.xsl"/>
> 
>   <xsl:param name="os">Mac</xsl:param>
> 
>   <xsl:template match="*">
>     <xsl:if test="not(@os) or @os=$os">
>       <xsl:apply-imports/>
>     </xsl:if>
>   </xsl:template>
> 
> </xsl:stylesheet>

For certain instances, I don't think that transform will always work
with the DocBook stylesheets as someone might expect.

For example, suppose I want to supply alternate MacOS and PC titles
for the "setting the timer" procedure:

  <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
    "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">

  <article>
    <articleinfo>
      <title os="PC">Starting the timer using Microsoft Windows</title>
      <title os="Mac">Starting the timer using MacOS</title>
    </articleinfo>
    <para>
      Press the <emphasis os="PC">Left</emphasis> mouse button to start 
      the timer. You can use the <emphasis os="Mac">Finder</emphasis>
      <emphasis os="PC">Start Button</emphasis> to launch a new program.
    </para>
  </article>

...and not that it matters in the case under discussion, but it is
valid to have multiple DocBook <title> elements in an <articleinfo>
section -- so the preceeding instance is not altogether artificial.

If I run that instance through the transform method you've outlined,
with no value specified for the $os parameter, it does not produce
what I would expect.

Specifically, I would expect the result to include the title with the
os="Mac" attribute by default -- but it doesn't. Instead, it simply
includes the first title, regardless of what attribute it has, and
regardless of the value of the $os parameter.

And although that one example may not be the best, there are other
cases where a DocBook instance + standard DocBook stylesheet transform
using that conditional inclusion method will not work.

I'm noting this only to make the point that it in this case of
conditional inclusion:

  * it seems problematic to rely on using templates that match
    specific element names
  
  * it would seem to be best to instead do a straight XML to XML
    transform based strictly on attribute names and values

...if that's even possible.

There must be some way to express it in XSLT...

-- 
Michael Smith          mailto:smith@xml-doc.org
XML-Doc                http://www.xml-doc.org/



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