Re: Nested Relations / RVAs / NFNF
From: Kenneth Downs <firstinit.lastname_at_lastnameplusfam.net>
Date: Wed, 27 Oct 2004 15:47:56 -0400
Message-ID: <c1uolc.gsf.ln_at_mercury.downsfam.net>
> appropriateness
>
> I'm following this with interest, although it's kinda unfamiliar ground to
> me.
>
> So, could you have two distinct types that share a common domain? That
> is, they both have exactly the same
> possible values, with the same semantics, but they don't allow the same
> operations on them?
Date: Wed, 27 Oct 2004 15:47:56 -0400
Message-ID: <c1uolc.gsf.ln_at_mercury.downsfam.net>
Laconic2 wrote:
>
> "Marshall Spight" <mspight_at_dnai.com> wrote in message
> news:17Rfd.316248$MQ5.24677_at_attbi_s52...
>
>> I note that in the type theory world, attention is paid to the
> appropriateness
>> of associated operations. For example, one might choose to have separate >> *types* for metric units and for English units, and allow the type system >> to either prevent invalid crossovers or convert for you. Also, you can do >> things like have a separate numeric type for speed, distance, and time, >> or even things like length, area, and volume. The type of the multipy >> operation for (length, length) is area; for (length, area) is volume, >> etc.
>
> I'm following this with interest, although it's kinda unfamiliar ground to
> me.
>
> So, could you have two distinct types that share a common domain? That
> is, they both have exactly the same
> possible values, with the same semantics, but they don't allow the same
> operations on them?
Wouldn't an overlap of allowed values be an artifact of the underlying storage type? If two types are both stored as int32 and have the range of -infinity to +infinity, they both share the same virtual domain and the same physical limited domain.
But methinks we'd be encouraged to think of that as a coincidence, and not to make much of it.
-- Kenneth Downs Use first initial plus last name at last name plus literal "fam.net" to email meReceived on Wed Oct 27 2004 - 21:47:56 CEST