Re: Codd provided appropriate mathematics ... (was Re: Relational and MV (response to "foundations of relational theory"))

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From: Marshall Spight <mspight_at_dnai.com>
Date: Thu, 04 Mar 2004 03:21:37 GMT
Message-ID: <1hx1c.37224$PR3.736500@attbi_s03>

"Bob Badour" <bbadour_at_golden.net> wrote in message news:84KdnZeYCbXcKKLdRVn-uw_at_golden.net...

> The question becomes: What are the operations on list values? If you think
> about the question for a while, you might find the answer unexpected.

Lists are a kind of relation, so certainly one wants to be able to treat them as relations.

List variables as they are typically implemented in programming languages are quite convenient to use, and can do an amazing amount. Also, their use in functional languages and the recursive techniques for handling lists are especially enlightening.

It would be nice if there was a convenient shorthand to say that a given relation was also a list. It would constrain the index column so that it was always in the range 0..count-1. Perhaps insert and delete operators adjust the index column? It's not clear what the right thing to do is.

On the other hand, it's also not clear whether the convenience factor of lists matters any more when you have the full relational algebra.

Marshall Received on Wed Mar 03 2004 - 21:21:37 CST