[uf-discuss] Cross-network identification (Was: OpenID)

Tue Feb 20 22:10:17 PST 2007

Scott Reynen wrote:
> On Feb 20, 2007, at 6:56 PM, John Panzer wrote:
>>> Scott Reynen wrote:
>> ...
>> Here's the purpose of UID from vCard:
>>> To specify a value that represents a globally unique
>> identifier corresponding to the individual or resource associated
>> with the vCard.
>>> So if two hCards have the same UID, they must refer to the same 
> person, because otherwise it wouldn't be globally unique. And I 
> think that solves the problem Thom described above, unless I'm 
> missing why it needs to be specific to OpenID.

Nope, it solves it. OpenID URLs are just one example.
> ...
>>> I'm thinking here of cases where the target may be an OpenID, but 
>> not necessarily provide an hCard.
>>> UIDs do not need to point to hCards. Nor do they need to be 
> OpenIDs. They can do both, but the only requirement is that they be 
> globally unique and correspond to the subject of the hCard. And that 
> minimal requirement seems to be just enough to solve this problem 
> without worrying about what, if anything, is on the other end of the 
> UID.
>Thanks. (The thread in the archives was somewhat twisty; the summary is 
helpful.) So, rel="url uid" it is.
I think this solves the problem of how to match one hCard up with 
another using a convenient unique key well above the 80% level.
One minor point: URLs are unique but not truly persistent. Due to URL 
reuse,when trawling through archives you can't assume that UID1 == UID2 
means person 1 == person 2 unless both UIDs were minted at the same 
time. I'd probably solve this heuristically if ever necessary, but: Is 
it worth an implementor's warning somewhere?
Interestingly, the vcard people seemingly dealt with this issue, because 
they edited [1] "persistent, globally unique identifier" prior to the 
final RFC draft.
-John Panzer
[1] http://www.imc.org/pdi/vcard-21.txt