SRN : I insist that subjects do have identity, but only within contexts -- within universes of discourse.I did not write something very different when I wrote that only representations can have identity. Maybe I should have put it slightly differently, and I'm sure Steve will agree with this other way to put it : Whatever the subject, it has neither absolute identity, nor absolute definition, nor absolute property of any kind, that would be valid in any context. Identity, and all properties bound to this identity, is always conferred through a representation, itself defined inside the context of some representation scheme, and making sense only in the framework of this scheme.
SRN: But I don't see how it's meaningful to say that a proxy is not a proxy for something in particular. By its very nature, a proxy is always a proxy for something in particular.Well here I think I disagree with Steve, if "something" is to be understood as "some thing". My view on this has always been that, for all practical reasons, it's the first act of "proxyfication" which brings the subject into existence, as a subject of conversation. But this debate is not really important, and we can proceed from here to the notion of subjects as blank nodes, with or without agreement on the separate existence of subjects. The original point of the debate set by Alistair and Dan was to know how to express in an efficient and meaningful way the fact that two or more representations in different schemes are somehow proxies for the same subject. My point was that this could be captured by something quite similar to an RDF blank node, lets' call it a Subject Blank Node, bearing no absolute identity, and of which only properties could be : represented this way here, and that way there.
The way I see it, a Subject Blank Node would have no logical property per se. It would not be part of any representation scheme, but would provide a hub between various schemes. Such a hub would allow applications able to make sense of several representations schemes, each with their specific structure and logical rules, to aggregate information from different schemes, such as a Topic in a TM application, a class in an OWL ontology, a concept in a SKOS scheme, a category in dmoz, a page in Wikipedia, a term in Wordnet, or a picture by Van Gogh, or a Nocturne of Chopin.