Bob Melson wrote: > 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. I think you were right the first time providing the relevant standards are being followed. See the discussion at http://en.wikipedia.org/wiki/Universally_Unique_Identifier Clearly any use of UUIDs would have to mandate the most recent standard, listed there, ITU-T Rec. X.667 | ISO/IEC 9834-8, or its successors. -- Ian The Hotmail address is my spam-bin. Real mail address is iang at austonley org uk

On Sunday 29 May 2011 09:57, Ian Goddard ([email protected]) opined: > Bob Melson wrote: >> 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 My original (erroneous?) contention was that identical data should result in identical UUIDs irrespective of where generated, so that Cousin Mortimer's record will produce the same UUID whether done on your machine or mine or somebody else's. As Wes pointed out, this effectively describes a checksum and, in honesty, I have to admit that that's very much how I conceptualized *IDs. It appears, however, that Cousin Mortimer's record will result in a unique ID on every machine on which a *ID is generated, so for N copies of the record on N machines there will be N unique identifiers. And that raises a question about the utility of those identifiers - if every one is unique, how do/can we know that they refer to the same record? The other component of my now thoroughly beaten-down original belief was that the *IDs were somehow akin to a digital signature, on the order of "none genuine without this ID". Assuming _that_ and that I've published my public key, anybody coming across ol' Mort's record anywhere could verify (1) that it came from me and (2) whether it's identical with the original. That obviously won't work with *IDs as they are at present. (Still, I find the idea of a per record digital signature attractive, tho' that's an entirely different topic for discussion). >> 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. > > I think you were right the first time providing the relevant standards > are being followed. See the discussion at > http://en.wikipedia.org/wiki/Universally_Unique_Identifier > > Clearly any use of UUIDs would have to mandate the most recent standard, > listed there, ITU-T Rec. X.667 | ISO/IEC 9834-8, or its successors. > Steamin' Ol' Bob (115 days without precip) -- Robert G. Melson | Rio Grande MicroSolutions | El Paso, Texas ----- The greatest tyrannies are always perpetrated in the name of the noblest causes -- Thomas Paine

On Sun, 29 May 2011 12:46:21 -0600, Bob Melson <[email protected]> wrote: >It appears, however, that Cousin Mortimer's record will result in a unique >ID on every machine on which a *ID is generated, so for N copies of the >record on N machines there will be N unique identifiers. And that raises >a question about the utility of those identifiers - if every one is >unique, how do/can we know that they refer to the same record? And if you merge two of those records, believing that they are same person, will the resulting record have TWO unique identifiers? -- Steve Hayes from Tshwane, South Africa Web: http://hayesfam.bravehost.com/stevesig.htm Blog: http://methodius.blogspot.com E-mail - see web page, or parse: shayes at dunelm full stop org full stop uk

On 05-29-2011 11:57, Ian Goddard wrote: > Bob Melson wrote: >> 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. > > I think you were right the first time providing the relevant standards > are being followed. See the discussion at > http://en.wikipedia.org/wiki/Universally_Unique_Identifier _No_. It is an algorithm designed to ensure that a UUID generated by any machine will never be the same as any other generated by the same machine OR any other machine. (Whether it meets that requirement is another issue.) Clearly that is in opposition to the desire for an algorithm that will generate an ID that _is_ the same as some other. What Bob wants is something most of us want, but few of us expect to ever get. But it is _not_ a UUID. -- Wes Groleau There are two types of people in the world … http://Ideas.Lang-Learn.us/barrett?itemid=1157