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Marshall agreed with me on something, so I'll dare post one of the many
questions I have related to relational database theory.
In Date's June 2003 paper entitled "What First Normal Form Really Means" he asks questions about MultiValue systems, which he (and no one else I've read) abbreviates as "MVS". I am preparing answers to these questions. Date writes "...MVS fields are ordered left to right (and so MVS files are certainly not relations, and the system is certainly not relational)."
I've been puzzled by this for quite a while, just figuring that relational theorists have this wrong. But the writings seem so sure of this. I had thought that the relations in relational database theory were mathematical relations, but I am beginning to think that might not be the case. My masters in mathematics was quite some time ago, so I hauled out some books and googled a bit and everything I find that is mathematics, rather than database theory, indicates what I thought about relations -- a relation is a set of ordered tuples -- right? What am I missing here? An element of a relation would be of the form (a1, a2, ... an) where a1 is an element of S1 etc. They ARE ORDERED LEFT TO RIGHT. Am I misunderstanding something or is there some other mathematical definition of "relation" that is the one on which relational database theory is based?
Thanks in advance for your help. --dawn Received on Fri Dec 26 2003 - 20:37:56 CST