Conditional actions in XSL?

[Richard Light]

In message <3.0.1.16.19980128075314.31f79096 at pop3.demon.co.uk>, Peter
Murray-Rust <peter at ursus.demon.co.uk> writes

>>>>Can any knowledgeable people help me clarify the followings:
>>>>
>>>>1. Does XSL supports either the above 2 scenarios (i.e. condition in
>>action
>>>>rules or processing descendants in scripts). I may overlook something.
>>>>
>>>>2. If neither of above is available in XSL, what are the good work around?
>>>>Will my 'hacking' work?

I don't know if a knowledgeable person can help, but meanwhile I'll have
a go ...

The conditions for XSL are set by the structure that you specify, e.g.:

    <element type="object">
        <target-element>
              <attribute name="REND" has-value="yes"/>
        </target-element>
    </element>

defines the target elements for a rule as being those elements which are
children of an "object" element, and which have a value set for their
"REND" attribute.  If the condition matches for an element, the rule
fires.  This is a pretty powerful mechanism, although it doesn't do the
'else' case you mention - that has to be another rule (perhaps a more
general rule - only the most 'specific' rule (3.2.6) applies to each
element).

I'm not sure about the ability to invoke a bit of script when testing
the attribute value.  The XSL spec allows you to invoke ECMAscript when
_setting_ attribute values on (output) flow objects - there is no reason
at all why it couldn't allow the same feature when _testing_ attribute
values on source elements.  (Obviously in this case the script would
have to return true/false rather than a string.)

When trying out a bit of code to show how easy this all is, I couldn't
get MSXSL to take any notice of an <attribute> statement inside a
<target-element> as per the above example.  But I think it should have
done!

One point is that the spec uses both 'name="XXX"' and 'type="XXX"' to
qualify <attribute> in its examples in 3.2.3.  I think, though, that the
'type="XXX"' is an error.  (Neither worked with MSXSL.)

Any more knowledgeable people out there?

Richard.

Richard Light
SGML/XML and Museum Information Consultancy
richard at light.demon.co.uk

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