Re: Using the catalogue

From: Jon Heggland <>
Date: Tue, 22 Nov 2005 10:36:50 +0100
Message-ID: <>

In article <>, says...
> Given: relation Person (Name, Weight, Designation, ... )
> If someone asked for all Persons whose Name was the same as their
> Weight, what would be your response ?

That depends on the domains/types of Name and Weight. If they are the same (not likely), or one can be coerced to the other, no problem. It depends on the domain definitions. It might be prudent to arrange for the system to issue a warning for such a comparison, though.

In any case, it should be no problem at all to ask for all Persons whose string representation of their Name matches the/a string representation of their Weight.

> On comparing Person.Name to Person.Designation: If "King" = "King" then
> is "King" = 'König" or 'König" = "King" ? 'König" is German for
> King.

Again, it depends on the domains/types and their implementation (though I think 'König" would be a syntax error---is it correct to mix single and double quotes like that in German?).

As for "King" being equal to both "King" and "König": your domain(s) might support values with more than one representations, just like integer values in most programming languages have two (or more) different representations, e.g. 13 and 0xD.

> Is comparing Persons.Name to Persons.Designation any different ? It
> might be amusing but not logical.

No difference. And it's logical; it might not be /useful/, though. But that is for the user to decide.

Received on Tue Nov 22 2005 - 10:36:50 CET

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