I think the identifiers are of the individuals in the context of specific roles within a larger institutional/social context. They are not identifiers of the roles themselves, since obviously many, if not all, individuals have these same roles.
MW: From a 4D perspective the identifiers are of the state of individual that is playing the role, rather than the individual for the whole of its life. For example, a Passport No. or a Driving License No only identifies particular states, not the person for the whole of their lives.
HP: Collective contexts have duration scope, so I do take a 4D perspective
Indeed, what identifiers of individuals are there that don’t have a specific context and perspective associated with them?
MW2: 4D is more than just accounting for time and change, it is a particular way to do it. The difference lies in the difference taken in the nature of individuals, and identity. A 3D approach says that an individual is wholly present at each point in time, whereas a 4D approach takes individuals as extended in time as well as space (so it is not wholly present at each point in time). Strong 4D goes further and says that the spatio-temporal extent is the identity basis for individuals, i.e. if two individuals have the same spatio-temporal extent, then they are identical.
MW: Sometimes identifiers are created with that purpose, a birth certificate number for example.
HP: But my point was that even birth certificates have a particular institutional context – and can get lost or destroyed. They don’t represent a context-free identity for a person and are typically not coupled directly to a person biometrically and not all have numbers. I don’t know of any system that uses birth certificate numbers as identifiers for people.
MW: How about the register of births? But I agree, identifiers are arbitrary.
That was why I made the comment “DNA notwithstanding” in my original post. By the way, DNA is not guaranteed to be a unique identifier, either – although evolution has endowed us with facial recognition capabilities that do a pretty good job. Maybe we will all live to see the day of a “context-free” individual identifier implanted in all individuals prior to birth? And what identifiers are inherent in individual entities that are not people? Maybe those laser-engraved serial numbers in some diamonds? Aren’t those put there by or under the aegis of a specific institution?
MW: Well this is a different point. The nice thing about unique identifiers is how many of them any individual can have. Being unique only means that within that context the identifier is managed to only refer to one thing. It does not prevent there being other unique identifiers for the same thing, and it does not prevent different identifiers for the same thing using the same scheme (though you might attempt that). For example, a person might try to obtain more than one Social Security Number so they can commit benefit fraud.
The point is that all identities
MW: Identity is different from identifier…
HP: Correct! But information systems generally don’t make that distinction because the only way they have of distinguishing among individuals is through identifiers – which have context, usually implicit and overlooked. And one purpose of the “entity primacy” principle is to make developers explicitly aware of that distinction so that they don’t mistake the identifiers they are using for individuals for the identity of those individuals (which is their own and inherent in their existence in some reality). The best we can do is to get socio-political agreement on some “near-innate” identifier for individuals, such as VINS for motor vehicles intended for use on public roads and MAC addresses for Ethernet devices. Such identifiers are useful for information sharing interoperability among diverse contexts about the same individuals. But we don’t really have such an identifier for people (yet). Maybe some “superDNS” identifier certificate issued independently of national/local jurisdiction before birth to all people (like VINs) will be brought about thanks to the Internet, but I’m not holding my breath. Or maybe some biometric will be found that can serve as this “near-innate” identifier on the network. And we need to be vigilant and remember that even these identifiers are not the same as identity and that the individuals may have other identifiers in other contexts.