Re: RA with MV attributes

From: paul c <toledobythesea_at_oohay.ac>
Date: Wed, 17 Jan 2007 14:58:11 GMT
Message-ID: <7Qqrh.691473$R63.173281@pd7urf1no>

David wrote:
> paul c wrote:
>

>>David wrote:
>>
>>
>>>...
>>>Why can't we say that *by definition* the set of attributes of a
>>>relation is part of its state not its type?
>>>...
>>
>>We can say anything we want "by definition", the question is where does
>>saying it get us?  What conclusions does it lead to and so forth.

>
>
> Marshall doesn't seem prepared to accept this definition on it face,
> because he has assumed that the set of attributes of a relation is
> surely its type.
>
>

>>I
>>like your suggestions because they seem to have something behind them,
>>but don't ask me what, exactly.  I wish you would distinguish whether
>>you are talking about physical implementations or user concepts.

>
>
> I guess this relates to the following discussion
>
> http://www.ai.mit.edu/docs/articles/good-news/subsection3.2.1.html
>
> I tend to think that both implementation and interface should be
> reasonably simple, and it's bad to strongly favor one at the expense of
> the other. I often look at what the implementation is telling me in
> order to design a reasonable interface. There is nothing better than
> getting your cake and eating it too.
>

That's a bit too blurry for me. What is simple as compared to what is too simple depends very much on the objective, as I think somebody said "as simple as possible, but no simpler!".

I do think that once one has a definition it is important to proceed to positioning it in the scheme of things, for example is this a physical approach for storing two relations in one or is it an attempt to promote three-valued logic or is it something else? I find this thread interesting because I think rva's have not been explored very thoroughly (perhaps they should be discounted eventually, but I don't think anybody has yet made a good case, or at least one I could understand, for this, yet).

The "advantage" of avoiding redundancy in general is also a blurred one for me. If the domain we're interested in is what cars certain people own, I don't find it all redundant that two people may happen to own the same kind of car. Whereas avoiding physical redundancy as far as computer machinery is concerned is a very worthy goal.

p Received on Wed Jan 17 2007 - 08:58:11 CST