Re: Proposal: 6NF
Date: 18 Oct 2006 03:46:10 -0700
Message-ID: <1161168370.499516.204970_at_i3g2000cwc.googlegroups.com>
David Cressey wrote:
> "paul c" <toledobythesea_at_oohay.ac> wrote in message
> news:g2iZg.155655$5R2.60964_at_pd7urf3no...
> > David Cressey wrote:
> > > "Tony D" <tonyisyourpal_at_netscape.net> wrote in message
> > > news:1161090234.533844.46810_at_k70g2000cwa.googlegroups.com...
> > >> paul c wrote:
> > >>
> > >>> Still, the bulk of the apps I've seen
> > >>> don't need that extended type support ...
> > >> I couldn't disagree with this observation more strongly. Without a rich
> > >> type system, we can't talk about the right things (attributes). If we
> > >> can't talk about the right things, we can't reasonably expect to
> > >> construct proper statements (relations). As well to make assertions
> > >> about horse racing by discussing camels :) And to have a rich type
> > >> system, we'd better make sure the underpinnings are at least consistent
> > >> and preferably correct ;)
> > >
> > > It seems to me that it's possible to talk about the right things with a
> rich
> > > domain system,
> > > even if lacking a rich type system. It also seems to me that user
> defined
> > > domains are not the same thing as additional types.
> > >
> > >
> > >
> > >
> >
> >
> > PMFJI, when it comes to a dbms engine, I don't know the difference
> > between a type and a domain.
> >
> In the context of a dbms engine, a type would be the built in datatypes
> that the engine supports, like INTGER, DECIMAL, CHAR, and DATE, and also
> the builtin functions and operations, like "+" or "weekday(x)".
>
> A domain would be what you get when you say CREATE DOMAIN. It's a set, but
> it has no functions and operations other than the ones it inherits from the
> data type it is based on.
>
> Does this make sense?
Hi David, I was previously under the impression that built in 'types' such as INT's or DATE's are domain s defined by a predicate, as opposed to being enumerated (e.g. tinyints := { x : x E Z, -128 < x < 128 } ), and I didn't distinguish them in my mind from user defined domains.
Are you differentiating a dbms type to a domain, in that a dbms type also has built in operations which apply to its domain definiton, and is this is a standard view? Cheers, Jim.
>
> > p
Received on Wed Oct 18 2006 - 12:46:10 CEST