Re: A different definition of MINUS, Part 3

Bob Badour wrote:
> vadimtro_at_gmail.com wrote:
...

>> Projection, is inner union in RL terms. Well, I don't see how to
>> represent inner union in terms of other operations:-(

 From the formal definition of <OR> (page 14),

Let s be r1 <OR> r2. It is required that if <A,T1> in Hr1 and <A,T2> in Hr2, then T1 = T2.
Hs = Hr1 union Hr2
Bs = { ts : exists tr1 exists tr2
( ( tr1 in Br1 or tr2 in Br2 ) and
ts = tr1 union tr2 ) }

If the '<OR>' is changed to say, '<INNER_OR>', and the third and last lines changed to read 'intersect' instead of 'union', wouldn't that be equivalent to RL inner union? Received on Mon Dec 22 2008 - 01:34:39 CET