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@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 Wed May 10 2006 - 21:29:07 CDT