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- From: "Michael Kay" <M.H.Kay@eng.icl.co.uk>
- To: "Peter Murray-Rust" <firstname.lastname@example.org>, <email@example.com>
- Date: Fri, 19 Dec 1997 11:50:04 -0000
Mark L. Fussell:
>I would strongly suggest first designing the genealogical object model
>from the GEDCOM definitions (and other sources) without considering XML
>or DOM at all.
Thanks, yes. I agree absolutely. Fortunately my background is in data
modelling so I'm happy with this side of things.
My design problem is whether to implement the genealogical objects as
pointers to XML DOM objects or as copies/conversions of data extracted from
DOM objects. Of course the choice can be hidden behind the interface.
>Any pure tree is extremely easy to represent in XML. So, if you simply want
>to trace an ancestor tree (i.e. two parents, 4 grand parents, etc.) this is
>The difficulty comes when the graph has cycles. I am not an expert
>genealogist, but most 'family trees' seem to me to be Directed Acyclic
>Graphs (DAGs) where the arcs are isParentOf(); and is directional. DAGs
>are common ...
Unfortunately the "family tree" is not isomorphic with the XML tree. There
no hierarchic relationship between a husband and wife. It isn't even a
DAG, (because I can record relationships like "A is-the-godfather-of B"
and "B is-the-executor-of A" ).
>Note that the use of ID/IDREF may introduce additional complexity.
>Personally I am not clear on the value of IDREF over XLL - it's not trivial
>to support in a browser and I doubt that JUMBO will do it.
I am currently using ID/IDREF to represent these relationships, because
it maps directly to the current GEDCOM standard. I still feel uncomfortable
that this is unrelated to the XLL linking model. I do recognise that
information in a genealogically-useful way is going to require application
logic, and won't be achieved by general purpose XML tools; though it
would certainly be nice if the general tools made it easy to follow ID/IDREF
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