Re: XQuery question

> Here there are no relations between relation T_Car and T_Color. Some
> might say T_Car has a "relation" to T_Color but this would not make
> sense in rdm-speak since a relation is defined as "a set of tuples".
> What formal word has rdm defined to described this type of "relation"
> between T_Car and T_Color?

The formal term is "Cartesian product". This is taken directly from set theory. This concept is sometimes also called a "cross product" (which is a slight misnomer), or a "product join".

neo55592_at_hotmail.com (Neo) writes:

> > >> Given meta-data tables that describe relations between tables, [...]
> >
> > > Since the relational data model (rdm) defines a "relation" as being a
> > > set of tuples which is generally conceptualized as a table, the above
> > > sentence in rdm-speak would translate to "tables between tables" which
> > > is probably not what you meant. What word did rdm formally assign to
> > > the word "relation" as used in the above sentence? Surely rdm has a
> > > formal word for that very basic and fundamental concept.
> >
> > He's obviously talking about entity tables and relation tables. See
> > any text on the ER (entity-relationship) model for more information.
>
> It is true that some relations are joined by having their foreign keys
> in a mapping relation that relates entities from two relations, and so
> in that case we could say "a relation between relations". But what
> about the case where there is no mapping relation involved between two
> related relations. For example:
>
> T_Car
> CarID
> ColorID
>
> T_Color
> ColorID
> Name
>
> Here there are no relations between relation T_Car and T_Color. Some
> might say T_Car has a "relation" to T_Color but this would not make
> sense in rdm-speak since a relation is defined as "a set of tuples".
> What formal word has rdm defined to described this type of "relation"
> between T_Car and T_Color?

-- 
Hopefully helpfully yours,
Steve
-- 
Steven Tolkin    steve . tolkin at fmr dot com   617-563-0516 
Fidelity Investments   82 Devonshire St. V4D     Boston MA 02109
There is nothing so practical as a good theory.  Comments are by me, 
not Fidelity Investments, its subsidiaries or affiliates.