Re: RA with MV attributes

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Wed, 17 Jan 2007 15:22:50 GMT
Message-ID: <ebrrh.1986$1x.32506_at_ursa-nb00s0.nbnet.nb.ca>

paul c wrote:

> Bob Badour wrote:
> 

>> Jon Heggland wrote:
>>
>>> David wrote:
>>>
>>>> Example
>>>>
>>>> r1(Names,Cars)
>>>> bill, car1,car2,car4
>>>> john,fred car3
>>>>
>>>> r2(Cars,Colours)
>>>> car1,car3,car4 red
>>>> car2 green
>>>>
>>>> r1 |X| r2 (Names,Cars,Colours)
>>>> bill car1,car4 red
>>>> bill car2 green
>>>> john,fred car3 red
>>>> john,fred green
>>>>
>>>> [...]
>>>> For example the
>>>> last tuple of r1 |X| r2 above doesn’t imply that John and Fred
>>>> don’t own any cars.
>>>
>>>
>>>
>>>
>>> So what exactly does that last tuple mean?
>>
>>
>>
>> And what would happen if we replaced (car1,car3,car4)<->(red) with
>> (car1,car3,car4)<->(red,blue) in r2 ?
>> ...
>
> Just curious, what does the symbol <-> stand for here?

Maps or relates. Received on Wed Jan 17 2007 - 16:22:50 CET