Re: Which is more declarative? More XMLish?

The direction of thought I have in mind has nothing to do with "constrained vocabularies". It has to do with an extension of our thinking about XML: the introduction of "semantic identity", as opposed to node identity; or to put it simply: the view that complex XML elements describe a thing (its properties), and that this description may be destributed over any number of element nodes. Introduction of a standardized way how to identify the thing - e.g. NIEM's @structures:uri attribute - enables the (semantic) equivalence of any distribution of a thing's description over one or more nodes. As a special case, the equivalence of a fully expanded child element and a child element containing nothing but its identity attribute becomes well-defined (assuming the content of the fully expanded version is found in other elements with the same identity value). As you see, the artificial "infinity" of the XML representation may vanish.

With kind regards,

Hans-Juergen

PS: I wonder if the W3C working groups have considered extending the XDM by a new node property which is an element node's "thing identifier" (IRI) - similar to NIEM's @structures:uri.