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   Re: [xml-dev] XForms Annotations (was Annotations in XPath-NG?)

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> I've been meaning to post something like this to xml-dev for awhile, now.
> XForms is probably a good data point to look at for XPath annotations, if
> I'm not misunderstanding the discussion.
> XForms is fully an XPath spec; brethren to XSLT and XPointer. As for
> annotations, XForms defines "model item properties" [1], such as "required",
> "relevant", "readonly", etc., which attach to the XPath 1.0 data model on a
> per-node basis. Form controls, which also attach to a particular node, alter
> their behavior based on the model item properties (which so far can all be
> represented as strings) at that node.
> >From an implementation standpoint, it would be nice to have a way to attach
> these extra properties to nodes.

The idea itself is similar to what we've been discussing here.  I don't think 
the binding mechanism defined in XForms is really suitable, since a general 
XPath processor would not add anything to the source document, nor is there 
really any place in the dat model for the bind elements themselves.

I also don't see in th XForms spec a mechanism for accessing bound properties. 
 Perhaps this is what leads to your next para...

> >From a standardization standpoint, it would be nice if XPath 2.0 included a
> way to access these properties. (We avoided defining accessor functions in
> XForms 1.0 because there are some non-trivial complications that can crop
> up, related to self-referential calculations, but that's firmly an XForms
> problem to solve)

In the general case, we seem to have two candidates: accessor functions and 
special axes.  Which one would you think works best with the XForms model 

> We were mainly looking a function-based access, though I suspect that's just
> because extension functions are easier to plug into an existing
> implementation (compared to, say, a new axis)

Yes.  My question above is more, if backward compat wasn't an issue, which way 
would you lean?

Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Apache 2.0 API - http://www-106.ibm.com/developerworks/linux/library/l-apache/
Python&XML column: Tour of Python/XML - http://www.xml.com/pub/a/2002/09/18/py.
Python/Web Services column: xmlrpclib - http://www-106.ibm.com/developerworks/w


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