Re: Objects and Relations
From: Joe Thurbon <usenet_at_thurbon.com>
Date: Thu, 15 Feb 2007 22:14:27 GMT
Message-ID: <7X4Bh.1630$4c6.1167_at_news-server.bigpond.net.au>
>
> Person is just a name for a predicate. Whether and how it describes
> anything in 'the real world' is part of the external predicate.
Date: Thu, 15 Feb 2007 22:14:27 GMT
Message-ID: <7X4Bh.1630$4c6.1167_at_news-server.bigpond.net.au>
Bob Badour wrote:
> Joe Thurbon wrote:
>> >> I guess I was thinking along these lines. Say, for example, social >> security fraud. When you see some tuples in some PEOPLE relation, with >> a primary key SSN. >> >> Person: {<SSN:12345, Name:"Fred">, <SSN:23456, Name:"Bill">} >> >> it is safe to assume that >> >> - there is an entity we are modelling, call him entity_fred, >> with a name "Fred", and >> an SSN 1234. >> No other entity exists with a SSN 12345. >> >> - there is an entiry we are modelling, call him entity_bill, >> with a name "Bill" and, >> an SSN 2345. >> No other entity exists with a SSN 12345. >> >> However, the relation, taken alone, does NOT mean that the entity_fred >> and entity_bill are distinct entities.
>
> Person is just a name for a predicate. Whether and how it describes
> anything in 'the real world' is part of the external predicate.
"External Predicate." I was not aware of that term. A quick google has helped me clear this confusion up.
Thanks.
> The dbms
> neither knows nor cares about the meaning of the word 'Person'. One
> could replace the name 'Person' with 'Hornswoggle' or 'x' and the dbms
> wouldn't care or notice. Hornswoggle would work exactly like Person.
>
Yes, I was aware of this part.
Cheers,
Joe
Received on Thu Feb 15 2007 - 23:14:27 CET