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   Re: [xml-dev] Still banging on about extensibility and validation

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> NVDL as a domain specific language is addressing the use case of validation of > extended documents, ...

I could be wrong, but I didn't think NVDL was just about validation of
extensions ?

I saw (see) it as providing an ability to apply validation processing
to individual parts of a document regardless of whether they are part
of a common specification or part of extensibility agreed between
communicating parties. My understanding is than NVDL facilitates a
slight change in the way that we can think about XML instances, from
one which considers the instance as a whole, to one which allows us to
view it as a set of related but individually processable parts ?


On 29/05/06, bryan rasmussen <rasmussen.bryan@gmail.com> wrote:
> >
> > >2. propogation of text nodes up from elements in namespace y to
> > >elements in namespace x, example:
> > >
> > ><x:x>
> > ><y:y>text node</y:y>
> > ></x:x>
> > >
> > >in this scenario y:y is extending x:x,
> >
> > But it is distinct.
> >
> > >and conceptually we assume that they share the text node.
> >
> > They do not.  In the data model for that fragment, x:x has three
> > children: two text nodes of only white-space, and one element node
> > being y:y ... the string "text node" is only a child of y:y.
> It seems that XML has a lot of different data models or has had a lot
> of different data models over the years. That this usage does not
> follow any data model for XML doesn't argue against the assumption to
> me, since what I'm arguing about is an assumption about common usages
> of extension.
> >
> > >so when split they should be
> > >
> > ><x:x>text node</x:x>
> > >and <y:y>text node</y:y>
> >
> > I disagree.  I don't know of any data model for XML in which text
> > nodes are "copied" or considered a property of an ancestor.
> >
> > >I think this is a reasonably common usage but I'm not sure if NVDL
> > >handles it.  I suppose the argument could be made that this is an
> > >extremely dangerous and dirty usage, and we would not want to automate
> > >that kind of splitting of data.
> >
> > On that I agree ... but since the data model does not "split" the
> > data as you describe, it fortunately isn't an issue for NVDL.
> >
> The argument is not that it should or shouldn't happen, but more
> questioning how far extensibility should go and what the needs for
> validation of extended documents are. NVDL as a domain specific
> language is addressing the use case of validation of extended
> documents, as such it has made decisions for handling various
> extension scenarios, if there are scenarios it skips then it should be
> argued for why they are skipped.
> I suggested one reason why one would skip that scenario is that it is dirty.
> I think in XML Schema some reasons why common validation scenarios
> were skipped was that they did not fit the theoretical model of XML
> Schema (this is just an idea on my end), and I think that is a good
> argument for a language to make (but if it is so in the context of XML
> Schema it just so happened my first ever use of it needed some of the
> missing validation possibilities, and this lack has not endeared the
> language to me, there can be tradeoffs between purity and necessity.)
> A third argument might be that, hey that scenario is hardly ever used.
> nobody asks for it.
> I think realistically NVDL is something needed for Compound documents
> type situations, but there are a lot of things needed in that
> situation.
> Cheers,
> Bryan Rasmussen
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