Re: object algebra
Date: Sat, 28 Feb 2004 23:44:00 GMT
Message-ID: <4J90c.81418$4o.104673_at_attbi_s52>
"Drago Ganic" <drago.ganic_at_in2.hr> wrote in message news:c1r4ku$dku$1_at_sunce.iskon.hr...
> Red, Green and Blue are colors."Not Applicable", "Unknown" are not. That is
> semantics for me .. that is something a painter or physics will understand.
This is true, but totally irrelevent to the question of recording eye color in a database management system. Can you mix green and blue eyes and cyan eyes? I think not. That is something any occular surgeon will tell you.
> I can >>mix<< Red and Green to get another color. If I mix Red and Unknown
> I get Unknown... That's the same problem we have now with 3VL
It seems you are confusing the operations on booleans with the operations on colors. One can keep the system entirely within 2VL and still have an atom "unknown" as a member of a set.
Further, eye color and abstract color are not the same types. If a user attempted to do color blending on two eye colors, that would indicate a type error to me, and I would hope the system could detect this condition with static analysis.
Marshall Received on Sun Feb 29 2004 - 00:44:00 CET