In an earlier post, Bernard talked about the thought that there is no identity, only identification process. Music to my ears.
In an earlier post of mine, I pointed to the TMRM, the new reference model for topic maps. Now, I would like to point to a plethora of presentations at coolheads.com, the website of Steve Newcomb and Michel Biezunski. In particular, the slides titled "What is a Topic Map Application (TMA)?". Roam about those slides and it may become apparent to some readers that subject identity is, indeed, a process, one in which the topic map author discloses the means by which topic identity is established and is to be compared where merging of topics is a goal.
My own interpretation, not putting words in anyone else's mouth here, is that the TMRM aims to make subject identity a center stage process, where portions of a subject's identity are established through assertions. Follow me closely here. Assertions replace the familiar associations of XTM, performing the same function of establishing typed, scoped relationships between topics. They then, under direction of disclosures, perform a role in contributing information to a subject's identity through castings. I prefer to think of the casting topics in light of my seeing as discussion earlier.
My present interpretation, then, is that subject identity is a dance. A process. I won't argue against the use of the familiar PSI (URI) notation for some objects in some universe of discourse. Indeed, we can all agree on the concepts "mother", "father", "sister", and so forth, and I'd be very happy to disclose that PSIs for concepts like those would suffice, no matter what language the name string for such topics turns out to be. But, in routine conversations, thought processes, and some written stuff, I, like many others, tend to orbit around subject identity, talking about "passengers in cars" and the like, contextually sensitive identifiers which may link back anaphorically to some other statement. It's often a composition of many statements, assertions, that leads to identity. It's a process.