Re: Database design, Keys and some other things

vc wrote:
> JOG wrote:
> > vc wrote:
> > >'The sky is blue in the daytime' ain't no predicate. It's an [ambiguous]
> > > proposition which could be false or true if it were not ambiguous.
> >
> > Ok. There exists a meteorlogical observation where [the sky is blue in
> > the daytime]. That is the sentence (not a very good one i'll agree, but
> > a propositional sentence nonetheless), with the predicate in square
> > brackets.
>
> Still not good enough. In logic, a predicate is a statement whose
> truth depends on the variable(s)ranging over some domains(s). E.g 'x
> is_older_than y' is a predicate, but 'John is older than Jim' is a
> proposition. You need to restructure your sentence some more in order
> to make a predicate out of it.

Ok, thank you for the correction. I'm using weak terminology in a very specific area (using predicate in terms of its grammatical meaning instead of math logic).

> > P = { <feature: sky>, <colour: blue>, <period: daytime> }
> >
> > M = { <creator: James>, <created: 1127871055>, <statement: P> }
> >
> OK. All the talk about predicates aside, why the piece of information
> above should be treated in a special way and called by the nebulous
> word 'metadata' ?

Yes talk of the terminology is a side issue. First I agree the term 'metadata' is woefully blurry, and given all data may be metadata and vice versa, its somewhat of a meaningless concept.

> What is gained by this in comparison to treating the
> additional attributes as part of the original entity (or being a
> separate entity) ?

Great question, and not one I'm sure I can answer yet - outside the fact that its mathematically correct to do so. Storing data _about_ a proposition in with the encoding of the proposition itself seems to me like attributing a quote to an author by putting his name inside the quote marks.

I mean, RM's still do a grand job, but given part of their allure is their theoretical correctness, it seems to me worthy of checking out as an area of possible improvement. Received on Wed Sep 28 2005 - 18:47:07 CEST