[xsl] Combining HTML/FO StyleSheets (Indirection/Abstraction Methods) - Non-Trivial

[Peter Bray <pdb_ml at yahoo dot com dot au>]

Greetings,  -- Sorry this is so long --

	I have developing some XSLT files to translate an XML document to HTML
and then moved onto creating XSL:FO translation of the same document. I
noticed the bulk of the complex operations are the same or very similar
for both style sheets and in order to avoid inconsistances I like to
merge the two sheets.

	Are there guidelines anywhere on developing such merged sheets?

	After slaving way at the problem I'll discuss below and coming up with
several non-working solutions, I was wondering "Do people create
intermediate markup languages to ease the generation of both HTML and
FO?" By this I mean do people generate and intermediate format (XML)
which has all of the complex processing completed, and then have
trivial conversion style sheets from that format to HTML or XSL:FO as
appropriate? ((Example: intermediate tag like <paragraph> -> <p> or
<fo:block> depending on the desired output format))

----------------------------------------------------------------------

	Anyway on to the actual problem. I have a tag I would like to generate
additional document content for, but I would like to be able to include
a level of indirection in that generation to make it general purpose
(ie not HTML or XSL:FO specific)

	I'll use a concrete example so it makes some sense :-) But the problem
occurs in other forms in the processing as well.

The XML
=======

  <versioninfo
     mode="RCS"
     filename="$RCSfile: Software.xml,v $"
     filerevision="$Revision: 1.12 $"
     filerevisiondate="$Date: 2002/01/29 12:24:53 $"
     timezone="GMT"
  />

Note: I have additional named templates to extract just the actual
information out of these RCS tags :-)

The Problem
===========

I would like to generate a simple paragraph whose contents are in
italics and in which the version number is in bold. Remember I'm trying
to solve a general problem here so don't get caught in the specifics.

Sample:
    Generated from RCS File Software.xml,v 1.12 2002/01/29 12:24:53
GMT.

The paragraph above is all or partially in italics and the version
number is in bold italics. OK. So as everyone can see this is not a
complex task in either HTML or XSL:FO - but how do I generate text with
a level of indirection to allow me to have high-level
output-mode-independent style sheets?

Solutions (or my failed attempts)
=================================

	The first thing I tried was to have named-templates called
"MakeParagraph", "Inline-Italics" and "Inline-Bold" (as you can
probably see this could be extended for most simple inline text
formatting). Each determines the type of out desired and places the
provided text (from with-param tag) inside the appropriate formatting
constructs and returns the result. Each of these work in isolation!!!
But if I try and nest the calls the tags (not the text) get stripped
(seemingly at the stage of passing the parameter in with <with-param>.
And just the result of nested calling is only the outer tags get
generated in the output.

Example:

    <xsl:call-template name="MakeParagraph">
      <xsl:with-param name="contents">
	<xsl:text>Text Here </xsl:text>
        <xsl:call-template name="Inline-Italics">
          <xsl:with-param name="text">
            <xsl:text>Italic Text Here </xsl:text>
            <xsl:call-template name="Inline-Bold">
              <xsl:with-param name="text">
                <xsl:text>Bold Italics Text Here</xsl:text>          
              </xsl:with-param>
            </xsl:call-template>
            <xsl:text> More Just Italic Text Here</xsl:text>
          </xsl:with-param>
        </xsl:call-template>
      </xsl:with-param>
    </xsl:call-template>

and in this case the greatly simplified HTML only named-templated

  <xsl:template name="MakeParagraph">
    <xsl:param name="contents"/>
    <p>
      <xsl:value-of select="$contents"/>
    </p>
  </xsl:template>

  <xsl:template name="Inline-Italics">
    <xsl:param name="text"/>
    <i>
      <xsl:value-of select="$text"/>
    </i>
  </xsl:template>

  <xsl:template name="Inline-Bold">
    <xsl:param name="text"/>
    <b>
      <xsl:value-of select="$text"/>
    </b>
  </xsl:template>

Result:
======

<p>Text Here Italic Text Here Bold Italics Text Here More Just Italic
Text Here</p>

Notice how the other tags have been stripped out of the result (this
happens on all three XSLT processors I have - xsltproc,xalan,saxon)

ANY THOUGHTS ????

Solution 2: Was to try and generate intermediate tags on the fly and
have them stuffed back into the processing stream (thereby deferring
HTML or XSL:FO generation) But I could not get this to work either and
it seems against the design goals of XSLT to process on-the-fly
generated markup recursively.

ANY THOUGHTS ????


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