Defining WebID: Reasons that WebIDs are not analagous to Passport Numbers

As we converge on a 2024 definition of a WebID, I thought I would write out
a source of some potential confusion, and also that it may inform our final
shared understanding of what a WebID

The analogy was that of a WebID and a Passport Number.  I've said here why
this analogy is not like-for-like, and hopefully illustrated some unique
properties of webid and its benefits.  Posting here for convenience so as
not to bloat an RFC thead:

https://github.com/w3c/WebID/issues/17#issuecomment-1888415378

Consider this: a passport number scribbled on a napkin loses its context –
it could be a passport number or perhaps a phone number. However, a WebID
inscribed on that same napkin retains its identity as a WebID, thanks to
the inherent universality of URIs.

The beauty of using URIs to name things, unlike mere numbers, is that WebID
plays a pivotal role in unifying the social web. A passport number is only
valid in the context of the passport it's associated with, and particularly
your passport. In contrast, if you place a URI in someone else’s document,
it contributes to the fabric of the web rather than causing ambiguity.

Moreover, for a direct comparison with a WebID, the passport itself would
need to serve as an identifier. A WebID is remarkable because, even when
noted in the most informal manner like on a napkin, it allows us to
retrieve the entire identity document. This capability is what sets it
apart – it’s not just a number. It’s special because it can reside in any
document, weaving a network of identifiers. It's special because of its
ability to be dereferenced, revealing not just the identity document but
also its place within that document, and crucially confirming its nature as
a WebID, denoting an Agent or a Person. This goes beyond a mere conceptual
analogy and enters the realm of practical, machine-testable functionality.