Simon Grant wrote: >> For instance if a book has been published several times, >> it's publication date is a set of dates. > > How do you square this with FRBR? I was not talking about FRBR but trying to answer your question. By the way I wonder how FRBR squares with reality - but FRBR is not the topic. > I wouldn't take seriously any proposed single entity with a > publication set of dates. Doesn't this mean that the entity > covers a set of other things each with their own publication date? No it doesn't. The choice what makes an entity is arbitrary and always an oversimplification of reality. If you don't want things to have multiple dates, you don't have to allow it, but either choice is not natural. > In which case, we have still not found a practical example of an entity > which, in its own right, has a set of dates as an attribute. Q: "When did this band play in your town?" A: "They gave a concert at 2nd and 3rd June" Q: "Oh, they started playing at 2nd and finished at 3rd?" A: "No, they gave two shows, one at 2nd, one at 3rd." Q: "But which date did they play?" A: "At 2nd, and 3rd, as I said." Q: "But '2nd and 3rd' is not a date!" A: "You definitely spent too much time with date formats!" Cheers Jakob P.S: Unless you try to relate sets of dates as "equal to" other concepts, like intervals, durations and single dates, the question whether to allow sets of dates is independent from other aspects, anyway. I would also forbid sets of cardinality less than two, to avoid more difficult questions. -- Jakob Voß <[log in to unmask]>, skype: nichtich Verbundzentrale des GBV (VZG) / Common Library Network Platz der Goettinger Sieben 1, 37073 Göttingen, Germany +49 (0)551 39-10242, http://www.gbv.de