On Thursday 26 May 2011 20:04, singhals ([email protected]) opined: > Tom Wetmore wrote: >> Cheryl, >> >> I stand corrected. I was talking about standard GEDCOM. The _UID tag is >> an extension tag used by some systems. As you say, UID's should be >> immutable for all time and space. But since it's not a standard tag >> there's not telling what might happen to it on import to arbitrary >> programs. Any program that changes its value on import should be taken >> behind the barn and shot. > > You could be right, but I would have sworn it was in the > GedStan. (shrug) I've been wrong before -- and /recently/. > > Cheryl Y'all'd have to check the archives for the down'n'dirty, but Wes and I and I don't remember who all else had a discussion of this very thing (_UID, _UUID, _GUID) some time back. I contended then that UUID (Universal Unique ID) and it's close kin, UID and GUID, meant that the number assigned to Cousin Mortimer should be the same universally - here, there, wherever it appears. Not so. The "universe" is the machine where the data appears and on which the software resides by which the UUID is generated and it's only there that it's guaranteed to be unique. Take that same data to another machine or other software and, guess what?, the Universal Unique ID will be different. Or, say, Mort's data changes - ta DA, you may (or may not) get yet another UUID. The only use I can see for UUIDs is in determining the origin of a particular record - if I publish Mort's data and include the UUID and some time later find that Snively Whiplash has published the exact same data with the exact same UUID and has claimed it to be his own, then I'll know what to think about ol' Snively, won't I? Swell Ol' Bob -- Robert G. Melson | Rio Grande MicroSolutions | El Paso, Texas ----- The greatest tyrannies are always perpetrated in the name of the noblest causes -- Thomas Paine