Re: On Formal IS-A definition
Date: Wed, 05 May 2010 03:49:54 -0300
Message-ID: <4be1151c$0$12433$9a566e8b_at_news.aliant.net>
David BL wrote:
> On May 5, 4:13 am, Tegiri Nenashi <tegirinena..._at_gmail.com> wrote:
>
>>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It is obsolete.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:-)
> > I agree. My own take on the Information Principle is that "one and > only one way" is misleading because one generally has a choice of > whether to use rich or simple domain types. One could represent the > entire database value in a single relation containing a single tuple > with a single attribute and be adhering to the Information > Principle. In that sense it seems rather vacuous.
I disagree that it's vacuous. Even in this situation, the principle prohibits physical pointers in the logical structure. Received on Wed May 05 2010 - 08:49:54 CEST