Re: object algebra

> > If we model various data examples, we should find less NULLs with TDM
> > than with RDM. For example, modelling 10 persons, each with different
> > properties.
>
> You're simply talking about an attribute of type PERSON,
> and the existence of multiple subtypes of PERSON.

Thus in RDM, the solution might appear as:

T_Person
ID
Name

T_PersonType1
Person_ID
Property1

T_PersonType2
Person_ID
Property2

T_PersonType3
Person_ID
Property3

... and so on, and additional new properties might result in new tables and algorithms would need to take that into account tables that didn't exist at time of coding.

The 10 persons are not really different sub types, the db is just being asked to store different properties for each.

> What does TDM allow you to do with those differing properties?

It does not require those extra tables (or any in fact). See www.xdb1.com/Example/Ex102.asp Received on Tue Feb 24 2004 - 01:19:49 CET