Ian, I certainly agree that the genealogical data model should be OO, consisting obviously of some entities (sources, events, persons, ...) with some well defined attributes (names, dates, places [if not entities], ...) and relationships. It's a classic ER/OO setup, and we'd be crazy not to exploit it as such. GenTech started as an OO model, but its leader was a relational database adherent, who insisted that instead of an ER model the GenTech model should be a set of fully normalized relational tables. For that reason alone I think GenTech died. (Well, and also the fact that EVERY fact had to be added with a separate ASSERTION record). A model should be a high level ER/OO model, not a model already customized for one particular representation in one kind of database. Personally, I think the network database is a much more natural database for genealogy -- you keep the beautiful and natural structure of the underlying ER/OO model, with no disadvantages as far as I've ever (20+ years of experience) found. I have used B-tree based databases for all my genealogical software and have gotten wonderful performance out of them. Well, the disadvantage is having to provide your own framework for searching, but this is not all that hard. In my original software, LifeLines, the database was nothing more than all the records kept in GEDCOM format, a GEDCOM that could be extended by whatever keys the user needed. It allowed all the GEDCOM record types, and allowed users to also define their own record types, though this feature was never used, and the program gives no support for it. In my current generation I am also keeping the OO records as the contents of the database, now in JSON or XML, and adding support for personas (same datatype as persons with no distinctions), multi-tierd person trees, event records, place records, and so on. LifeLines was written when I was a junior genealogist, fully steeped in the person-based or conclusion-based ethos. But now I have reached the point in my genealogical life where I have thousands of "unattached" items of evidence I am sorting through, and I MUST get that data into a database in the form of personas just so I don't go insane searching through unorganized pieces of paper, index cards, and image files on my computer. As personas, the data is indexed, sortable, searchable and manipulable in many ways. Think of a persona as one of those old-style index cards with all the index holes punched all around them (look up McBee edge-notched cards on Google -- the physical analog of all associative memory systems! -- I LOVED those things when I was a kid, fifty years ago -- see http://www.kk.org/thetechnium/archives/2008/06/one_dead_media.php ). Stick your needle in different holes and your personas get sorted by name, by date, by place, by residence, by occupation, by whatever. Lots better than looking at certificates, pages in city directories, pages in family history books! Tom Wetmore

Tom Wetmore wrote: > Think of a persona as one of those old-style index cards with all the index holes punched all around them Been there, done that! Back in the days when I worked in labs we had a system based on those for identifying wood fragments under the microscope. You bought the booklet, a stack of printed cards & a notch cutter and cut cards from the list in the booklet, one card for each species. -- Ian The Hotmail address is my spam-bin. Real mail address is iang at austonley org uk