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Re: [xml-dev] Holographic XML

When we were working on the XML design of Universal Business Language at
least one contributor thought our design was too '2-Dimensional' and we thought
we might be able to improve things by using substitution groups (we were self-
constrained within what could be achieved with W3C XML Schema version 1).
Some thought a kind of polymorphism could be achieved this way which would
help with customizing at schema level
We abandoned this (in UBLv2) due to weaknesses found in how XML Schema 1.0's
substitution groups worked (and were implemented) but there remains a thought
that if we had RelaxNG we might have achieved this kind of 'holy grail' polymorphism.
I suggest it might be worth looking at how RelaxNG might provide an alternative to
substitution groups and allow the XML it constrains to be more '3D'.

Best regards

Stephen D Green

On 7 September 2010 16:46, Costello, Roger L. <costello@mitre.org> wrote:
Hi Folks,

Just brainstorming ...


1. Holography is where the information about the 3 dimensions is stored in 2 dimensional space.

2. I've been told by industry experts that if you're not in the 3-D memory business in four years, you're not going to be in the memory business.


Operating in 3 dimensions seems to be something that will be increasingly important.

XML is kind of a 2 dimensional representation of data. How can XML expand to 3 dimensions?


Here are two responses from colleagues:

3-D storage is really only about increasing the size of an array.  There's no additional complexity, only increased space organized differently.

byte [1024][1024] twoD;
byte [1024][1024][1024] threeD;

Notice that the addressing and storage method are basically the same, but "threeD" is undeniably way bigger.

This analogy doesn't really carry over to XML.  You can't "increase the space" or density of an XML document, because it's already arbitrary according to the user's whim.  The only way I can possibly think to carry over the analogy to XML is to increase the "degrees of freedom" in an XML document by abandoning the hierarchy/rooted-tree constraint, and making it possible to represent arbitrary graphs.  (After all, trees are only a special case of graphs)  We can already do this today with RDF and other XML-serialized graph representations.  Notice that unlike 3-D storage, this introduces different semantics, not just another array dimension.  Good for some things, not for others.


I agree with David.  Along the notion of additional "degrees of freedom," check out "Colorful XML: One Hierarchy Isn't Enough" by Jagadish et al.:







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