Steve, I would like to know what you have in mind, saying:
"Unless I misunderstand you, Hans, SGML has always had this. As far as I
can see, XML still has most of it, amid a storm of deprecation by those
who don't accept the fundamental distinction between "a homogeneous
space of [all?] information" and a SYSTEM that provides access to some
portion of that space."
My position is that XML implicitly creates a global space of information, a space which *is* a space (= something providing for "location" and "movement") because of XPath. I view XML and XPath - the models of representation, of information content, of content navigation - as a single unit, facets of which are syntax, data model, navigation model.
Consequently, I am very curious in which respect you perceive a space whose essence is probably not XPath - because you refer to SGML. So if I have understood you correctly and you do perceive a space of information, I would like to learn more about this view.
One more remark. When you think about the semantics of addresses I suppose you mean links - one resource referencing other resources via links. But the space I am thinking of is not dependent on linking - it favours linking, as it enables the resolving of links - but it is not created by links. Links are but a way of using the space. The space I am thinking of is in the first place a navigational potential: the possibility to unambiguously address any single node in a worldwide forest, and to translate this addressability into apparent motion, navigation.
Hans
