On May 13, 8:11 am, "Peter J. Seymour" <[email protected]> wrote: > That is why in the Gendatam system an event can be standalone or linked > to any number of people and/or evidence records and can have any number > of dates. Thanks for pointing out the Gendatam data model. That's a new one on me, and I'll definitely spend some time over the weekend reading up on it. > It is however in my experience rare for an event to be > assigned more than one possible date. I think it depends a bit on how you use it. Lots of sources -- censuses, gravestones, marriage certificates to give a few examples -- give the age of a person which allows you to infer the date of birth to within a year. But it's not uncommon, in my experience at least, for these ages to be wrong. Often it's unlikely that I'll find a precise date of birth, but it's convenient if programs can display an approximate date -- for example, so I can easily distinguish in a list of names between John Smith (b c1650) and John Smith (b c1800). Most software doesn't seem to do this automatically, so it's sometimes worth adding birth events for them. But if you do, then you have to deal with incompatible data. In the case of a birth, we know that a person is only born once, so the program can infer that if there are multiple birth events in the database, they must all be talking about the same real-world event. A program could come up with a good way of presenting the incompatibility -- perhaps by coming up with a range like "b c1810-12". But there are other events that are not guaranteed only to have happened once. Take a marriage, for example. If there are two separate marriage events between person A and person B, this could mean several things. Perhaps most likely, two reports of the same real-world event, maybe with incompatibilities due to errors in the sources. But perhaps the couple had two marriage ceremonies, maybe in different religious traditions if the couple were of mixed religions. Or perhaps the couple married, got divorced and remarried -- unlikely, but possible. So for marriages (and many other events), we need to be able to say whether we believe that two events in the database derived from different sources are describing the same real-world event. The Gentech data model copes with this. In the same way that personas can be grouped together to say "I believe these three sources are describing the same John Smith", we can use groups to say "I believe these three sources are describing the same marriage". > The links are scoped as > Gentech-style assertion records that help tie down probabilites. > However, I should point out that this sort of thing can get rather > complicated if it is pursued to its logical conclusion. Perhaps so, but I'd like to think that a program can hide a lot of the complexity from the user, except in those cases where it's important. Richard