On Fri, May 26, 2006 at 05:25:49PM -0400, A. Rick Anderson wrote: > Gordon Clarke wrote: > >Isn't the Open Source community great. > > > >Thanks Paul for another example of generating guids!!! > > This algorithm doesn't seem very close to the DCE/IETF/OSF standard: > http://en.wikipedia.org/wiki/UUID. > > Once you pay the price for 128 bit key, it seems rather silly not to use > a standard that just about always will guarantee uniqueness. > > I may be off base here. I wrote a Java implementation of the ISO > standard several years ago, and at that time, the standard didn't > support multiple algorithms.
You obviously know more about this that I do, since I am merely using the Data::UUID implementation on CPAN, but as I understand it, this implementation is based on http://hegel.ittc.ku.edu/topics/internet/internet-drafts/draft-l/draft-leach-uuids-guids-01.txt which seems to be an early version of http://www.ietf.org/rfc/rfc4122.txt which is referenced on the wikipedia page you mentioned. Now the first document specifies a UUID "is either guaranteed to be different from all other UUIDs/GUIDs generated until 3400 A.D. or extremely likely to be different (depending on the mechanism chosen)". The second specifies that the UUID "can guarantee uniqueness across space and time". Since the latter claim is obviously impossible in a finite number of bits, (and since I've not investigated the matter in detail), I'm unsure whether the algorithm has changed or whether some marketdroid got to the rfc between these documents. But a quick scan of the rfc does seem to allow for the possibility of multiple algorithms anyway. > The current Java implementation, Java 5, now ships with a UUID class > that seems to be somewhat compliant, but follows Sun's abysmal practice > of explicitly violating Liscov's substitution principle. Bah, OO is for wimps. Don't you know that the future is functional? ;-) -- Paul Johnson - [EMAIL PROTECTED] http://www.pjcj.net _______________________________________________ Ldsoss mailing list [email protected] http://lists.ldsoss.org/mailman/listinfo/ldsoss
