RE: Dynamic XSL

["Maddison, David" <Ma...@dnb.com>]

This sounds really good, where can I get more hardcore information on XSLT,
all the books I've picked up so far only 'skim' XSLT as part of an XML
technology, however after playing with it, I can't believe how powerfull it
is!

The reason I think I need XSL is because in my publishing system the style
sheet is built up using different objects.  For example the page object gets
called, which adds it's data to the XML document and then it's formatting to
the XSL.  The page object then has a list of all the objects on the page,
each one has it's chance to add it's data and then it's XSL formatting, and
so on down the tree until all the data, and all the XSL processing
instructions have been fetch.  They are then put through the reactor,
generating the final document.

The thing is all the objects are added to pages dynamically, so for example,
there may be a Module object on the page, there may not.  In order to do as
you suggest, and use parameters, I would have to have a stylesheet that
contained ALL the object formattings, which would be a bit of a pain in the
butt, both to administer and code, as well as slowing down the XSLT
processor.

On certain sheets I also have objects placed in certain positions within the
page template.  The objects are chosen based on an ID attribute, for example
there could be 3 Module objects on the page, each containing different
contents, however they each have a unique ID attribute.  I then tell the
XSLT processor where to place the Modules using the following syntax :

<xsl:template match="/">	
	<table width="100%">
		<tr>
			<td valign="top">
				<xsl:apply-templates
select="Module[@ID='1']"/>
			</td>

			<td valign="top">
				<xsl:apply-templates
select="Module[@ID='2']"/>
				<xsl:apply-templates
select="Module[@ID='3']"/>
			</td>
		</tr>
	</table>	
</xsl:template>

Maybe all this CAN be done with parameters, and I just need to read a good
book.  On a thinking note, could XSL get it's parameters from the XML
document?  If so that might put a completly different spin on things, as the
required object formatting could be dynamically Imported?

Certainly interested in the new design documents for Cocoon if anybody has
them, (ie the pipeline approach), it may save me replicating work!

David Maddison

-----Original Message-----
From: Simon Waddington [mailto:simon@viafone.com]
Sent: 30 August 2000 20:43
To: cocoon-dev@xml.apache.org
Subject: RE: Dynamic XSL


I have a feeling you haven't explored the capabilities of XSLT far enough.
You can do some extremely complicated stuff with it and it is easy to modify
the XSLTProcessor to pass in environment as style sheet parameters.  Or you
could dynamically generate a stylesheet fragment consisting of parameter
declarations that is included into a main stylesheet.   The main stylesheet
then modifies its behaviour based on the parameters, just as any other piece
of code would.

I have yet to think of a problem complicated enough to require dynamic
generation of XSLT that couldn't be solved with parameterized stylesheet
behaviour.  But I do see the need to execute code before the stylesheet is
processed to determine what those parameters should be - that's exactly what
XSP and the processor pipeline is for.  Heck you can even pass date to XSLT
without modifying the processor at all - just get some XSP to add extra top
level nodes (PI or otherwise) containing styling info into the output tree.
Your XSLT then reads these and modifies its behaviour accordingly.

-----Original Message-----
From: Maddison, David [mailto:MaddisonD@dnb.com]
Sent: Wednesday, August 30, 2000 2:57 AM
To: cocoon-dev@xml.apache.org
Subject: Dynamic XSL


Cocoon is cool, especially as a proof of concept, definitely proves that
XSL/XML based publishing systems can work fast enough, even faster than some
'old world' systems I know.

Although the cocoon framework allows me to hook in my own producer, (which
is cool!), it doesn't allow me to hook in my own XSL producer, which is
something required for a true publishing system.

Why would you need this?  Well consider a users home page, similar to My
Yahoo.  The user can decided on an indivdual layout, but the data behind is
exactly the same, so in this case I want the data to be created, however I
want the ability to dynamically create the XSL for layout, based on a users
preferences.

A full web system, (similar to Allaire Spectra or Vignette), is something
I'm speccy out at the moment.  It'll problably use Cocoon as the publishing
engine, (with my own producers, etc), but provide all the other things
Cocoon doesn't, i.e. User profiling, Content Objects, Role based security
etc.

Would also be cool if the producers etc could be 'Bean'effied' that way the
engine could be distributed over several EJB servers!  I'm thinking maybe
the request could  be split into two threads, one that goes and gets the
formatting, and one that goes and gets the data, both merging to produce the
final result.

David Maddison
Yahoo IM : maddisondavid
Jabber IM : davmad@jabber.org