Re: A Logical Model for Lists as Relations
From: Jay Dee <ais01479_at_aeneas.net>
Date: Thu, 11 May 2006 02:29:07 GMT
Message-ID: <Tjx8g.34028$P2.3888_at_tornado.ohiordc.rr.com>
>
>
> If one has a numeric index that differs for each tuple, one never has
> duplication. If one has duplication, one wonders how to refer to the
> duplicates. As Codd observed long ago, once one has said a thing is
> true, what does saying it again achieve?
>
>
> I still do not know what sort of requirements would cause me to want a
> list in the first place.
Date: Thu, 11 May 2006 02:29:07 GMT
Message-ID: <Tjx8g.34028$P2.3888_at_tornado.ohiordc.rr.com>
Bob Badour wrote:
> Jay Dee wrote:
>
>> Bob Badour wrote: >> > Since it is relatively easy to write a query that extends a relation >> > with a rank per any explicit order, I am not even sure the ordinal >> > attribute is required. >> >> True. I wasn't exactly sure what MS wanted to happen, for example, >> to the fourth element in a list when the second element is elided. >> Does it become the third? If so, your proposal is a good >> solution. But... >> >> What if he envisions a list in which duplication of elements is >> significant?
>
>
> If one has a numeric index that differs for each tuple, one never has
> duplication. If one has duplication, one wonders how to refer to the
> duplicates. As Codd observed long ago, once one has said a thing is
> true, what does saying it again achieve?
Yes, I agree. If one were, for example, compiling a list of what folks were going to bring to the picnic, it might be nice to know that potato salad had been recorded many more times than fried chicken...
> In that case - and I'm supposing that's what MS
>
>> had in mind - a relation of element values wouldn't work. >> >> "More requirements, please!" >> >> In the end, though, I'm confident that the lists MS desires can be >> implemented in a relational design without inventing anything beyond >> what already exists.
>
>
> I still do not know what sort of requirements would cause me to want a
> list in the first place.
...but significant data - and information opportunities! - are lost if that's all you record.
In that regard, I agree: lists provide nothing more than relations do and carry opportunity costs. Received on Thu May 11 2006 - 04:29:07 CEST