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From: bbanerje@sjuvax.UUCP (B. Banerjee)
Newsgroups: net.ai
Subject: Re: Use of "and"
Message-ID: <254@sjuvax.UUCP>
Date: Thu, 12-Apr-84 18:51:48 EST
Article-I.D.: sjuvax.254
Posted: Thu Apr 12 18:51:48 1984
Date-Received: Sun, 15-Apr-84 05:45:44 EST
References: <551@sri-arpa.UUCP>
Organization: Saint Josephs Univ. Phila., Pa.
Lines: 52

>> There is another way of looking at the statement -
>>  all customers in Indiana and Ohio
>> which seems simpler to me than producing the new phrase -
>>  all customers in Indiana  AND all customers in Ohio
>> instead of doing this why not treat Indiana and Ohio as a new single
>> conceptual entity giving -
>>  all customers in (Indiana and Ohio).
>> 
>> This seems simpler to me. It would mean the database would have to
>> allow aggregations of this type, but I don't see that as being
>> particularly problematic.
>> 
>> Jim Cowie.

My admittedly inconsequential contribution to this.

all customers in Indiana AND all customers in Ohio seems to want the
following :

(Pardon the Notation!)
[all customers such that |
	{customer C- Indiana} XOR {customer C- Ohio}
]

This seems to be described best as
[all customers such that |
	customer C- {Indiana U Ohio - (Indiana (~) Ohio)}
]

Assuming that no customer can be in Indiana and Ohio simultaneously,
the intersection of the sets would be NULL.  Thus we would have
[all customers such that |
	customer C- {Indiana U Ohio}
]

Here, Indiana and Ohio correspond to sets of base type customer.
C- denotes set membership and (~) is intended to denote set
intersection.

So far so good.  However, the normal sense of an AND as I understand
it, corresponds to a set intersection.  The formulation is therefore
counter-intutive.

I'm not an AI type, so I would appreciate being set straight.  Flames
will be cheerfully ignored.

Regards,
-- 


				Binayak Banerjee
		{allegra | astrovax | bpa | burdvax}!sjuvax!bbanerje