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Re: [xml-dev] XPath and a continuous, uniform information space

On Thu, Aug 15, 2013 at 2:29 PM, Hans-Juergen Rennau <hrennau@yahoo.de> wrote:
Michael, Uche,

referring to Michael's words:

Come to think of it, perhaps the problem is more that we equate an "XML document" to a "web resource". What we perhaps need is a way of distributing a single XML document over a large collection of web resources, and then navigating around that XML document seamlessly, using XPath?

Of course we can do that crudely already, using entities or XInclude. Perhaps we just need a smarter implementation of transclusion, where the document fragments are fetched on demand when XPath navigation needs them, rather than being assembled eagerly by the XML parser.

it seems to me that this is *exactly* the idea pursued by the approach "super-documents / seamless navigation" sketched in an earlier posting. Or am I mistaken? I would like to know. Differences? Directions in which to seek improvement?

See below...

Super-documents as a view
What I find very interesting is the possibility to *impose* a super structure on a given set of documents, integrating them into a single logical tree. The super-document is essentially a *view* imposed on a set of documents. Having accomplished this, one may alternatively deal with the documents in the conventional way (as independent entities), or in a novel integrated way, navigating the super-document. In the latter case, overall navigation can be viewed as the merging of two kinds of movement, moving within the super-structure from "part" to "part" (where parts are documents, physically), and down into the "parts". And this is exactly the behaviour mimicked by the example, which navigates the tree-structured catalog and then drills into the documents.

It's probably the use of "documents" above which prevented me from thinking of yours and Michael's documents in the same way.  As I understand Michael's quote, it's not just a convenient view ver existing documents, but fundamentally redesigning what "XML document" means, at least for this limited scenario.  Rather than documents I would think of the component bits as more like general entities or XInclude fragments.  In my opinion what Michael is proposing is in effect redesigning the fundamental behavior of an XML parser whereas what your super-documents idea is doing is layering some additional, useful capability on top of XML parsers as they already exist.

When I mentioned that I wanted to spend the weekend thinking of Michael's idea, it was primarily with MicroXML in mind.  The charter of the MicroXML group allows us to consider the complete redesign of the XML parser, never mind just tinkering with XPath semantics.  Mind you, that doesn't mean I'd suggest allowing the MicroXML parser to automatically trigger requests of Web resources.  That would be a backward step after we've closed some important security holes by eliminating entities and DTDs.  Rather it might be a matter of having some sort of hook/callback mechanism based on node patterns.  Someone else could then layer on that, at their own risk, a handler that traverses Web resources?  All unformed thoughts, for the moment.

Uche Ogbuji                       http://uche.ogbuji.net
Founding Partner, Zepheira        http://zepheira.com

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