Re: Complement in Relational Lattice

On May 31, 6:58 pm, paul c <toledobythe..._at_oohay.ac> wrote:
> Marshall wrote:
>
> > So offhand I would expect de Morgan's to hold for
> > RL complements.
>
> > This one's for you Paul. ;-)
>
> Thank you Marshall. Somewhat mixed feelings as I was hoping to spend
> the summer getting some old scooters on the road and now I'm obligated
> to achieve a better understanding of the RL ideas.

Don't give up on the scooters too easily. :-) All algebra and no scooters makes Johnny a dull boy.

> I must admit that I
> didn't try very hard to understand RL ages ago, but was intrigued by its
> approach to union, thinking that it might be a very practical engine
> technique. Changing one word in the D&D Algebra definition would give
> the same operator, admittedly that would pervert their analogy and which
> was pointed out directly by others and indirectly too (I remember Jon H
> talking about predicates that get truncated, can't remember exactly what
> he said, truncated is my word, not his, still that didn't bother me).

In a way I can't articulate yet, I sense that the attribute truncation (which was kinda weird for me at first) is actually a virtue, or rather, a necessity, when one gets to the embedded logic and the inference rules thereof.

> I
> am guessing that part of their resistance has to do with the very name
> "union" even though they suggest the name "disjoin" for the version that
> parallels conventional boolean algebra. Has the same result when
> headings "match", so I was surprised that people found it out-of-sorts
> with D&D, since the latter stipulate that over and over anyway!

Heh. I call the two operators "and" and "or" and write them "&" and "|"
and that makes pretty much no one happy! But the connection with boolean algebra and logic is too strong for me to ignore.

Plus, I really like the idea of having a separate set of operators for the relational vs. the scalar operations. Don't know what I'm going to do about =, though. :-) Or relational division.

Marshall Received on Fri Jun 01 2007 - 05:48:52 CEST