Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]
From: VC <boston103_at_hotmail.com>
Date: Sun, 3 Jul 2005 09:29:20 -0400
Message-ID: <Iv6dnSxFcci5dVrfRVn-ig_at_comcast.com>
Date: Sun, 3 Jul 2005 09:29:20 -0400
Message-ID: <Iv6dnSxFcci5dVrfRVn-ig_at_comcast.com>
"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
news:I4Cxe.135796$Bh7.7066690_at_phobos.telenet-ops.be...
> Jon Heggland wrote:
[...]
>> Not personally, but what more do you need than definitions of value,
>> domain, tuple and relation, and a minimal set of algebra operators?
>
> The notions of database schema, database constraints, database instances
> and how they are exactly related.
A constraint (in the RM) is just a predicate [required to evaluate to true].
A relation schema is a schema name R and a set of attributes A: R(A)
A relation instance for R(A) is a set of tuples.
>
> -- Jan Hidders
Received on Sun Jul 03 2005 - 15:29:20 CEST