Re: Interpretation of Relations
Date: Mon, 22 Jan 2007 22:00:22 GMT
Message-ID: <Wtath.4146$1x.69551_at_ursa-nb00s0.nbnet.nb.ca>
Joe Thurbon wrote:
> On 2007-01-22 23:39:14 +1000, Bob Badour <bbadour_at_pei.sympatico.ca> said:
>
>> Joe Thurbon wrote: >> >> The RM includes the operations on relations by which one does the >> inferencing. Does it not?
>
>
> Depending on how you interpret relations into predicates, I would say
> that JOIN and PROJECT are kinds of inferencing rules. But they seem
> quite different to modus ponens.
But is functional dependency so different from modus ponens?
>>> Anyway, I've rambled on quite a bit. The ideas are pretty new to me, >>> still in development, and really, I'm getting ahead of myself because >>> I still don't fully understand the RM. >> >> Would the observation that the relational calculus is basically 1st >> order predicate logic help you understand it better?
>
> Not really. Well, I guess its validation that I'm not completely crazy.
> I was actually starting from the assumption that the relational calculus
> could be embedded in 1st order logic.
>
> I will feel like I understand the RM when I can answer the question: for
> a relational theory (by theory I think I mean a set of relvars - a set
> of 'instantiated' relations), what is the corresponding logical theory
> (set of grounded wffs).
Do you include the constraints as expressed by wffs in the set of relvars?
> I have other questions, too, of course. What does it mean to close a set
> of relations under consequence? (Is is the repeated application of JOIN
> and PROJECT?)
I think you might find your answer stuffed away under the subject of predicate inheritence or inference especially wrt views.
What is the analog of, say, material implication?
Isn't that just intersection? Or am I misreading something?
What is
> a valid implication? What parts of logical consequence do I lose when I
> represent my knowledge in a relational form.
>
> I appreciate that these are probably basic things, but I'm really having
> trouble finding any information on it, so I'm just working my way
> through it. I'll probably understand it better this way anyway, although
> references would be appreciated.
>
> Cheers,
> Joe
>
Received on Mon Jan 22 2007 - 23:00:22 CET