Re: atomic
Date: Tue, 06 Nov 2007 16:44:01 GMT
Message-ID: <lR0Yi.181614$Da.140829_at_pd7urf1no>
paul c wrote:
> David BL wrote: > ...
>> Is this what you mean (in Prolog):
>>
>> r(Name,Car,Colour) :- Name owns Car with Colour.
>>
>> r1'(Name,Car) :- r(Name,Car,Colour).
>>
>> or in natural language
>>
>> r1'(Name,Car) :- there exists Colour such that r(Name,Car,Colour).
> ... > > I think so.
By the same token,
r1'(Colour) :- there exists Name, Car such that r(Name, Car)
et al, ie., applies to all combinations of projections.
I think of these as symmetrical REFERENCE'ing statements and they are
implicit from the choice of attributes of a relation. For me, this
means that the orthodox view is that the form of optional data must
involve more than one relation. So if set-valued attributes are
eligible in the orthodox framework, I think I'd want to be able to say
similar sentences about them.
The snippet above doesn't mention the types of Name, Car, Colour. I think there is a difference between saying the type of Car is set of elements and the type of Car is a subset of those elements and if I understand correctly, David is talking about a Car attribute which allows subsets as values (as I have been too). Received on Tue Nov 06 2007 - 17:44:01 CET