[xsl] Assigning a dynamic value of href in a stylesheet PI

Hi Folks,

I have a stylesheet which outputs an XML document, containing a
stylesheet processing instruction (PI).  I would like for the PI to be
customized to the client.  (I have a different stylesheet for each
client.) 

For example, if the client is Internet Explorer, then the PI should be:

<?xml-stylesheet href="MSIE-parts-styler.xsl" type="text/xsl"?>

If the client is Netscape, then the PI should be:

<?xml-stylesheet href="Netscape-parts-styler.xsl" type="text/xsl"?>

And so forth.

I pass into my stylesheet a parameter, client, which indicates who the
client is.  Since the list of clients will grow over time I don't want
to have to hard code into the stylesheet all the clients.  That is, I
don't want to do this:

<xsl:template match="/">
    <xsl:choose>
        <xsl:when test="$client='MSIE'">
            <xsl:processing-instruction name="xml-stylesheet">
                    <xsl:text>
                       href="MSIE-part-styler.xsl" type="text/xsl"
                    </xsl:text>
            </xsl:processing-instruction>
        </xsl:when>
        <xsl:when test="$client='Netscape'">
            <xsl:processing-instruction name="xml-stylesheet">
                    <xsl:text>
                       href="Netscape-part-styler.xsl" type="text/xsl"
                   </xsl:text>
            </xsl:processing-instruction>
        </xsl:when>
    </xsl:choose>
</xsl:template>

Ideally, I would like to do this:

<xsl:template match="/">
    <xsl:processing-instruction name="xml-stylesheet">
         href="{concat($client, "-part-styler.xsl")} type="text/xsl"
    </xsl:processing-instruction>
</xsl:template>

Where client is the name of the parameter that is passed into the
stylesheet.

Alas, this later approach is not possible (because the contents of
xsl:processing-instruction must be text).

Does anyone have a good solution for this?  That is, one that doesn't
force me to add a new xsl:when clause every time a new type of client
comes in.

OFFTOPIC: Does anyone know how a HTTP header indicates that the client
is Netscape (as opposed to IE)?  The HTTP user-agent header field
contains MSIE if the client is IE.  If the client is Netscape there
doesn't seem to be any way of identifying that the client is Netscape. 
Any ideas?

Thanks!  /Roger


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