paul c wrote:
> Bob Badour wrote:
>
>> paul c wrote:
>>
>>> David Cressey wrote:
>>>
> ...
>
>>> But I'm also thinking that when you say 'project a relation onto its
>>> attributes', if such a thing were permitted by some RM impl'n, what
>>> *could* actually happen is that a relation with a single
>>> relation-valued attribute would be formed and I suppose that
>>> attribute's 'type' would be the name of the relation. But join is
>>> usually the operator we expect to be able to undo a projection, so if
>>> an impl'n did this, then I suppose it might want to undo the
>>> rva-creating projection, and that might entail that it also have a
>>> way of equating a relation with several attributes against a
>>> single-attribute rva equivalent.
>>
>>
>> Such as the relational equality operation?
>
>
> Yes, but I suspect when I come up with examples, some trouble/ambibuity
> will show up.
>
>>> In this admittedly oddball view of things, I wonder if the name of an
>>> rva really matters? That's as far as I've got.
>>
>>
>> What's oddball about it?
>
>
> I wasn't clear - I didn't mean the rva can have any (unique) name we
> choose, just wondering if there are times when an rva could be unnamed
> without risk - that's what I meant by oddball.
If an attribute has no name, how are we to refer to it?
Received on Mon Sep 25 2006 - 08:36:13 CDT
