Re: [xml-dev] Holographic XML

[Norman Gray <norman@astro.gla.ac.uk>]

Greetings.

On 2010 Sep 7, at 19:15, Peter Hunsberger wrote:

> On Tue, Sep 7, 2010 at 12:54 PM, Micah Dubinko
> <Micah.Dubinko@marklogic.com> wrote:
>> XML is 1-dimensional. It is defined as a sequence of characters. This is true even of, for example, an SVG document.
>> 
>> There is no need for XML to "expand" to more dimensions, though higher-level layers might come in to play.
> 
> I'd disagree: a sequence of characters is a lower level representation
> than XML; XML adds semantic and syntactic representation on top of
> that and gives you much more than a "sequence of characters."

XML above the character level is no more one-dimensional than it is two- or three-dimensional (nor has it a non-integer dimensionality).  It's a serialisation of a tree (which may or may not imply some more general graph), and as such I doubt it is mathematically sensible to talk of a dimensionality at all.

The terms 'dimension', 'fractal' and 'hologram' are precise ones, and while it is sometimes useful to use them as analogies, in this case the analogies are so very loose, that I think it extremely unlikely that an argument which rests on them can come to any useful conclusion.

XML is a tree.  That is a hugely flexible data structure, and there is a startling range of things (of varying dimensionalities!) which can be represented that way, and which can therefore be usefully serialised as XML.  But not everything can be usefully represented like that, and the harder you have to work to cram something into a tree, the poorer is the XML part of that 'solution'.

Sometimes, just occasionally, in extreme cases, XML is not the answer.

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk