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From Stefano Mazzocchi <>
Subject Re: [RT] Cocoon Blocks and internal web services
Date Fri, 29 Mar 2002 10:20:31 GMT
Greg Weinger wrote:
> > But this is not enough: behavioral description *depends* on
> > the type of the exposed resource.
> >
> > For example, a resource such as
> >
> >  block:skin://xslt/document2html
> >
> > will have to expose the returning MIME-type (XSLT in this
> > case) as well as it's schema, as well as the schema of the
> > conten that it's capable of transforming and the schema of
> > the content that is capable of generating after the transformation.
> How difficult would it be write code that automatically generates these
> "entry" and "exit" xml schema contracts for a stylesheet?

Well, honestly I don't know: everything I start thinking about something
like that I don't even reach half of the complexity that my minds blows
up and you know I'm not that new to high level abstractions :)

But it seems to me it's probably one of the most complex things *ever*
in the realm of structured languaged, but I'm wide open to suggestions.

> The block
> deployment code could create them for you.  For hard-coded components,
> it's up to the developer.
> The converse would also be useful; like a generic unit test for a
> stylesheet, based on these "entry" and "exit" schemas, it would
> determine if the stylesheet "satisfies" the contract.
> I am working on a cocoon application with dynamically pluggable
> stylesheets that needs something like that.  Without any kind of
> validation, the system is just too brittle, and anyone who writes a bad
> stylesheet can wreak havoc.

Yes, I'm totally aware of this, but I'm not sure you understand the
complexity of the problem. Suppose you have something like this:

 A -> [1] -> B

where A,B are two XML documents and [1] is an XSLT stylesheet.

The first thing to say is that the validation engine must be namespace
capable, this automatically rules out DTDs. My personal suggestion,
since this is a validation phase and shouldn't mess with the infoset,
would be to use RelaxNG.

But other than that I get stuck :/

Scott, Norm, do you have any useful information for us on this subject?
I mean: did you guys in the XSLT WG ever thought about 'validating' the
stylesheet behavior against a pipeline flow rather than validating the
stylesheet *itself*?

Stefano Mazzocchi      One must still have chaos in oneself to be
                          able to give birth to a dancing star.
<>                             Friedrich Nietzsche

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