[xsl] controller stylsheet. performance, best practices question

[Terence Kearns <terencek@xxxxxxxxxxxxxxxxxxx>]

In an application I'm building, I've found myself applying an MVC 
pattern to how I call templates. I have once stylesheet used by all my 
web-based server scripts (PHP scripts). This website then calls 
different templates based on the context of the script.
Here is the script, questions to follow:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet
    version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>

    <!-- import templates implementing dynamic content -->
    <xsl:import href="xsl-inc_finder.xsl" />
    <xsl:import href="xsl-inc_subjects.xsl" />
    <xsl:import href="xsl-inc_requirements.xsl" />
    <xsl:import href="xsl-inc_listing.xsl" />
    <xsl:import href="xsl-inc_login.xsl" />

    <!-- set context used by the controller -->
    <xsl:param name="op" select="'<?php echo @$_GET["op"]; ?>'" />

    <!-- BEGIN MAIN PAGE TEMPLATE-->
    <xsl:template match="/">
            <!-- blah blah blah. masses of literal content goes here -->
<!-- CALLS TO THE MAIN CONTENT BEGIN HERE -->
                <xsl:choose>
                    <xsl:when test="$op = 'finder'">
                        <xsl:call-template name="finderPage" />
                    </xsl:when>
                    <xsl:when test="$op = 'subjects'">
                        <xsl:call-template name="subjectsPage" />
                    </xsl:when>
                    <xsl:when test="$op = 'login'">
                        <xsl:call-template name="loginPage" />
                    </xsl:when>
                </xsl:choose>
<!-- CALLS TO THE MAIN CONTENT END HERE -->
            <!-- blah blah blah. masses of literal content goes here -->
    </xsl:template>
    <!-- END MAIN PAGE TEMPLATE-->

</xsl:stylesheet>



Functionally, this appoach seems to work well for me. My questions is:
Is taking this sort of approach prone to big performance problems?
I can see that in many cases, most of the templates imported at the top 
of the style sheet will not even be used. They can't be included on the 
fly because they need to be top-level (can't be nested inside IF or 
CHOOSE).*

Any other observations about the merits of this approach appreciated.

cheers.

* I could probably use PHP code to include it on the fly, but I want to 
avoid doing so because I've made a rule for myself not to use 
server-side code embedded in the stylesheet. I've done so in the param 
of this example for purposes of clarity, normally I would send them to 
the processor directly from the PHP function call.


--
Terence Kearns: Web Developer
University of Canberra: +61 2 6201 5516



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