Yes, you're right, it is a three-way association with 0-1 instances of activity. From a database perspective, repository-source is an associative table - no primary key only foreign keys. So it would be useful for performing queries on various combinations of the foreign keys.
I think the three ids (activity, repository, source) serve to identify a specific search. In Activity/Search, activity-id is a primary key. Each record defines one of three possible kinds of searches: 1- source without a known repository (search for a repository?) 2- repository without a particular source in mind (search for sources?) 3- a source known to exist in a specific repository (normal search) On the other hand, repository-source is indexed by the three ids. If a repository has several copies of a source, then a given search in one of those copies, would require a separate repository-source record to store the call number, etc. If you were interested in which copies (call-numbers) of the source you had looked at in a repository, a query of just those repository-source records which match repository-id and source-id would give that info. -Stan --- BTW, I'm a software engineer in the San Francisco bay area. Genealogy is a side interest of mine. I have studied the gdm spec and have an idea to represent it using UML. My background is more in C++, OOP, and systems programming. XML is still new to me. Hans Fugal wrote: >hmm, that's an interesting perpsective. This made me look closer at >repository-source, and I am a little muddy now... > >It looks like repository-source ties 0 or 1 repositories to 0 or 1 >sources to 0 or 1 activities (searches). It seems to me that this opens >the door for data redundancy - there could be (and I think would be) >many searches in one repository/source combination. But with >repository-source as it is we have to duplicate not only the repository >and source ids, but also the call-number and description. I don't see >why search has repository-id and source-id and repository-source has >activity-id. Why not take activity-id out of repository-source, leaving >it only to link repositories and sources, and take out the >repository-id and source-id from search? What am I missing - why did the >Lexicon Group do it this way? > ><hans/> > >* Stan Mitchell [Tue, 9 Jul 2002 at 10:35 -0700] ><quote> > > >>A few thoughts on repository-source ... >> >>IMHO & from an OO point-of-view, repository-source seems to be a >>separate class. It represents the association between no or one instance >>of source and no or one instance of repository, with the constraint that >>there be at least one source or one repository. When a search succeeds, >>then a source and repository are tied together, and information such as >>call-number and description of the condition of the particular source, >>are stored in the repository-source instance. >> >>Another way of looking at it, is as the link between the Administration >>and Evidence submodels, but with perhaps a closer link to Admin. >>Maybe <repository-source> could be a child of <search>. >> >>Stan Mitchell >> >>Hans Fugal wrote: >> >> >> >>>One repository exists in one place, so it seems natural to make >>>repository a child element of place. I've also made place-part a child >>>of place for the same reason. >>> >>>The GDM calls for a sequence number on each place-part of a place, and >>>an ordering scheme of the place-parts of a place. With XML order matters >>>(unless we say it doesn't) so I see no need for a sequence number; it is >>>implied. >>> >>>On those many-to-many relationships: repository-source isn't as clean >>>cut in my mind as source-group-source was, and now I'm not as clear >>>about that either. For one thing, the naming becomes hairy. Naturally >>>we don't want to make source a child element of repository, because a >>>source could exist in more than one repository; the other way around >>>is even more ludicrous. So, we need to reference the sources in the >>>repository or reference the repositories in the sources. So I think >>>perhaps: >>> >>><source id="film0049002"> >>> <citation-part citation-part-type="film">0049002</citation-part> >>> <repository-source idref="fhl"/> >>></source> >>> >>>That name, "repository-source", makes perfect sense in database context, >>>but I think it's confusing in this context, where it is a child element >>>of the source element. Perhaps "repository-ref". >>> >>>Maybe we can even allow a repository-source element from either a source >>>element or a repository element - that may be harder to deal with in >>>implementation though, and there is no way to avoid the possibilitiy of >>>duplicates. So my question for anyone who has an opinion is which is >>>better: to put it in one of the elements (i.e. a source element has a >>>repository-ref child element), or to have a separate (non-child) >>>repository-source element? >>> >>><hans/> >>> >>> >>> >>> >>> >> >> >>_______________________________________________ >>gdmxml mailing list >>[EMAIL PROTECTED] >>http://fugal.net/cgi-bin/mailman/listinfo/gdmxml >> >> ></quote> > > > _______________________________________________ gdmxml mailing list [EMAIL PROTECTED] http://fugal.net/cgi-bin/mailman/listinfo/gdmxml
