Re: On Formal IS-A definition
Date: Tue, 4 May 2010 13:13:50 -0700 (PDT)
Message-ID: <c8ed64e3-d25c-4b1a-9956-479717d640cd_at_r21g2000prr.googlegroups.com>
On May 3, 5:04 pm, paul c <toledobythe..._at_oohay.ac> wrote:
> ... and never bring up,
> say, just what the Information Principle really means.
..."the entire information content of the database is represented in
one and only one way. Namely as explicit values in column positions
(attributes) and rows in relations (tuples)."?
It is obsolete.
Seriously, I think it is aimed at cowboys who try to invent new data
management systems without studying what relational model is about. It
is about attributes and tuples because both relational calculus, and
algebra explicitly refer to relations structured this way. The
situation is similar to arithmetic where pupils learn how to add/
multiply numbers represented in a very specific notation. So the
arithmetic principle would say ..."the entire content of arithmetic is
represented in one and only one way. Namely as explicit sequences of
digits in numbers". Presumably arithmetic principle would prevent some
from reinventing roman numerals:-)