Re: A Logical Model for Lists as Relations

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Thu, 11 May 2006 23:08:27 +0200
Message-ID: <4463a7b2$0$31638$e4fe514c@news.xs4all.nl>

Vadim Tropashko wrote:
> mAsterdam wrote:

[snip]

>>So, we have several ways to describing a list as a relation, at
>>least "numbered items" and "successive items".

>
> The difference between the two essentially reduces to the way how we
> represent the order. The first method is intensional. It encodes the
> elements of a list with integer numbers which are (totaly) ordered. The
> second method is extensional. The order is represented explicitly by
> binary relation.

ISTM both ways are encodings of the list order. In "numbered items" beyond that we see an encoding of each of the items in the list.
In "successive items" the relation is recursive.

But how does intensional vs. extensional discriminate between the two? Could you please elaborate? (I didn't find a suitable definition - maybe someone could provide a link?)

>>To me it isn't clear what discrete piece of information content
>>is carried by an individual "number" or "successor" attribute.

>
> This question is meaningless without understanding what "information
> content" is.

As meaningless as the information principle, right?

          The entire information content of a relational database
          is represented in one and only one way: namely, as
          attribute values within tuples within relations.

		-Chris Date in
                "EDGAR F. CODD 08/23/1923 – 04/18/2003 A TRIBUTE"

> ... Arguably, sequence is even more frequently
> occuring concept than set. There is even a
> dedicated website dedicated to integer sequences:
> http://www.research.att.com/~njas/sequences/

Thank you for your reply and for the reference. Received on Thu May 11 2006 - 16:08:27 CDT