Re: Objects and Relations

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 26 Feb 2007 14:59:59 GMT
Message-ID: <PBCEh.1520$PV3.21889@ursa-nb00s0.nbnet.nb.ca>

Alfredo Novoa wrote:

> On 24 feb, 13:43, "Cimode" <cim..._at_hotmail.com> wrote:
>

>>If you define class by domain then what is the RM equivalent for
>>relation?

>
> You probably mean the OO equivalent for relation.
>
> OO lacks an equivalent for relation. That's why it is so difficult to
> write database applications using OO languages.
>
>

>>In RM, a domain is *not* the same* as a type or a relation.

>
> In RM domain is used as a synonym of type and it is completely
> different to relation.

The above is arguable and depends on one's definitions for domain and type. Specialization by constraint makes them essentially synonymous.

>>(
>>domain = set of *possible* values for which a relation draws
>>*possibly* values

>
> When you say "relation" we assume that you mean "relation value". If
> you mean "relation variable" please write: "relation variable" or
> "relvar".
>
> On the other hand, a domain is a set of any kind of values: scalar,
> relational, tuple, array, etc.
>
>

>>typing  = making a domain from a relation body and name (therefore
>>only *existing* values for a specific relation).

>
> I don't see any sense here.

As usual, Cimod uses a definition derived solely from his own imagination. Received on Mon Feb 26 2007 - 08:59:59 CST