Re: Idempotence and "Replication Insensitivity" are equivalent ?
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 25 Sep 2006 13:36:13 GMT
Message-ID: <hXQRg.38682$9u.331691_at_ursa-nb00s0.nbnet.nb.ca>
> ...
>
>
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> Yes, but I suspect when I come up with examples, some trouble/ambibuity
> will show up.
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> 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.
Date: Mon, 25 Sep 2006 13:36:13 GMT
Message-ID: <hXQRg.38682$9u.331691_at_ursa-nb00s0.nbnet.nb.ca>
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 - 15:36:13 CEST