Re: what are keys and surrogates?

From: David BL <>
Date: Wed, 9 Jan 2008 08:07:25 -0800 (PST)
Message-ID: <>

On Jan 9, 1:25 pm, Marshall <> wrote:

> This issue goes away if we relax 1NF and allow attributes that are
> lists or relations. This gives us nested structures. (Nested relations
> are not particularly controversial around here.)

In addition to my previous post, I wish to add another comment regarding my suspicion with RVAs. The tuples of a relation are supposed to represent facts, but what does it mean when a relation merely represents a value? Isn't the RM meant to have some close association with FOPL?

It seems to me there is a fundamental difference between

  1. a large collection of propositions relevant to a particular UoD; and
  2. a composite data structure such as an AST which simply "is what it is"

IMO the RM is very practical for a) but not generally suitable for b).

If you want to describe a composite data structure indirectly using a large collection of propositions then expect to need to go on a naming spree in order to refer to the parts of the data structure that are related to each other!

If on the other hand you use nested relations to directly represent the data structure (so as to avoid the need for meaningless identifiers) then you're not even choosing to represent it using a large collection of propositions at all, and that is contrary to what the RM is all about. Received on Wed Jan 09 2008 - 17:07:25 CET

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