Re: Data Metrics

ferrante formato (formato@bridge.diima.unisa.it)
Sun, 26 Jul 1998 18:07:47 +0200 (MET DST)

Camilo wrote:
>
> Hi,
> does anyone know about approaches to theories on the definition of
> a metric for data?
>
> Something like measuring the "distance" between two records, based
> on the data they contain, NOT on the repository (their "physical" distance
> on a hard disk plate, which wouldn't be that sensical anyway).
>
> Please, I know this is an uncharted terrain, so communication is not so
> straight forward.
> Telling me ... "use fuzzy logic".. when a metric theory approach hasn't
> been defined for a fuzzy set is not helpful.
>
> If you have thought about it, what could mean it?
>
> Thanks
>
> Camilo
>
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I think that the distance between two records is a subject that
can be using the duality between similarity and distances, (which has
been hugely investigated) provided that you identify
a record scheme having n fields with an n-ary predicate.
You identify a record scheme with an atomic formula. Then each ground
instantiation of the formula is a record:
example

automobile(Ford_Fiesta,1978,20000km,3000$)

this is a record and a ground predicate, at the same time.
again
automobile(Y_10,Autobianchi,1989,80000km,4000$)

Now, for each field, (or domain attribute) you define a similarity (or,
accordingly, a data-metric)
If you take the minimum (Or any continuous t-norm) of the similarity
degree among data in the fields,
you get a similarity degree among the records.
Finally, you compute
the distance according to the corresponding metric, and you have done.--
Bye
Ferrante Formato
Dipartimento di Ingegneria dell'Informazione e
Matematica Applicata
Universita' di Salerno
Phone : +39.89.965269
Fax : +39.89.964191
e-mail formato@udsab.dia.unisa.it

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