Re: Tree (forest) design

"Neo" <neo55592_at_hotmail.com> wrote in message news:4b45d3ad.0403081108.1972e241_at_posting.google.com...
> >
> > Trees can be generalized into tables, but the reverse is not true.
>
> The actual structure used to store the data, whether it be a table or
> tree can usually generate any view such as a table, tree or 4D. The
> actual storage structure optimizes a model for some views at the
> expense of being less efficient for others.
>
> For example, RDM's internal data structure (aka relation) optimizes it
> for generating tabular views while making it less efficient at
> generating tree-like views.

Not at all. Trees are handled quite easily with relations. The only issue is the missing "generalized transitive closure" operator that Date et. al. call for. Some vendors have their own version of something like this, such as Oracle's "connect by."

> Conversely, a model whose internal data strucuture uses trees
> optimizes it for generating tree views while making it less efficient
> at generating tabular views.

Yes, this is true.

Marshall Received on Wed Mar 10 2004 - 05:32:48 CET