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Home -> Community -> Usenet -> comp.databases.theory -> Re: Nested Sets And Pedigrees
In article <c0d87ec0.0204051000.79ec9d8b_at_posting.google.com>, 71062.1056
@compuserve.com says...
> >> Make two trees:
> - a mother-tree where X is a child of Y if Y is the mother of X,
> and
> - a father-tree where X is a child of Y if Y is the father of X. <<
>
> I am not sure that would work. Consider a family of several
> generations with both sons and daughter. Fred is the father of
> (Sally, Tom); Fran is the mother of (Sally, Tom). When Sally gets
> married and has a grand-daughter, which tree is her child put into?
>
> This is not really a tree, but a graph structure. Maybe a table of
> (father, mother, child) rows would work better.
What I currently thought of doing, until I read about your elegant nested set posts, was to have a table Person, a table FamilyLink and a table LinkRole. I then thought maybe I could apply nested sets instead, but it seems to not be the case. There are many potential complications that prevent you from making clean tree-like representations. Primarily, looping can arise due to consanguineous mating (inbreeding).
Oh well, I guess this is something best left to the application layer...
(Any opinions expressed are strictly mine only and not my employer's)
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