Re: object algebra

"Neo" <neo55592_at_hotmail.com> wrote in message <news:4b45d3ad.0402241230.1365e6a5_at_posting.google.com>...

> Because the basic representational block in RDM is "rectangularish",
> to represent 10 persons each with different properties without NULLs,
> one has to resort to additional tables. The need to "subtype
> attributes" in this case is artifical and brought on by NULLs, which
> RDM creates, not reality.

NULL was brought on by the primitive data type system in SQL DBMS', not anything intrinsic to the relational model, as I'm sure has been explained to you before. NULL can and should be abolished, in favor of user-defined data types which can include "special" values, if so desired, with user-defined semantics, like IEEE floating point's NAN and +/-INF.

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Joe Foster <mailto:jlfoster%40znet.com>  "Regged" again? <http://www.xenu.net/>
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