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

"Eric Kaun" <ekaun_at_yahoo.com> wrote in message news:k6r%b.50112$LX2.42031_at_newssvr33.news.prodigy.com...
> As an aside in this discussion, I've seen "multivalued" defined 2
different
> ways in explanations of relational (some of which are really bad).
>
> 1. Where attribute A can hold a list of values (type LIST)
> 2. Where there are attributes A1, A2, A3, A4 (for example), all of the
same
> type and meaning. For example, ADDR1, ADDR2, etc.
>
> Does 1NF refer to both of these? If not, what's the proper terminology for
> each of these cases?

Good question because it is likely clear to most data folks that 1, which is the one more often referred to as multivalued (there is a MultiValue trademark associated with one such model) and is not permitted by the relational model, is a much better strategy than 2, which is permitted.

I don't think there are any theories related to data storage and retrieval that would suggest that 2 is good design, but relational data modeling in practice is much more likely than others to promote this poor approach so that data is in 1NF (as if that were so dog gone important). smiles. --dawn Received on Thu Feb 26 2004 - 20:31:31 CET