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Re: Little question for RDM theoristes

From: Erwin <e.smout_at_myonline.be>
Date: 16 Jun 2006 00:49:29 -0700
Message-ID: <1150444169.031575.20840@c74g2000cwc.googlegroups.com>

U-gene wrote:
> Two relations (relvalues) exists. These relations have different
> headers (schemas). Are these relvalues the values of different types?

Yes.

> IMHO all relvalues have the same type

Yes, too.

> and the headers is just data. May
> be it is special kind of data which is different from rel.bodies' data.

No. The heading is not data. For if it were, one logical consequence would be that you would have to be able to "update" it (the header part of the data) in some way. But what does that do to a relation value ? What operators would do that sort of thing ? Would such an operator have side-effects on the relation body ? etc. etc. In their most recent edition of the Manifesto, Date/Darwen have a chapter on nonscalar type inheritance. I haven't read it that far yet, but I presume that their ideas are that any specific relation type is a subtype of some "generic" relation type. Therefore, each relation value is of more than one type at the same time : its most specific type RELATION{somespecificheading} and its generic type RELATION{nospecificheading}. Received on Fri Jun 16 2006 - 02:49:29 CDT

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