Re: Guessing?

From: David BL <davidbl_at_iinet.net.au>
Date: Thu, 24 Jul 2008 07:54:14 -0700 (PDT)
Message-ID: <8f91db82-8f47-40b4-be47-d54eb4451e91@v1g2000pra.googlegroups.com>


On Jul 24, 9:25 pm, "Brian Selzer" <br..._at_selzer-software.com> wrote:
> "David BL" <davi..._at_iinet.net.au> wrote in message
>
> news:cf134a05-1096-4a43-b1fb-c4c45e03eb42_at_c65g2000hsa.googlegroups.com...
>
> > On Jul 24, 10:56 am, "Brian Selzer" <br..._at_selzer-software.com> wrote:
>
> >> > In a database encoding there is only a single defined interpretation
> >> > of the encoded attributes as values in the RM formalism. Therefore
> >> > there is no distinction between symbol and value that can be made.
>
> >> I don't agree. Under the domain closure, unique name and closed world
> >> assumptions, a database is a proposition that is supposed to be true.
> >> How
> >> the database is physically implemented is irrelevant.
>
> > A relation is formally defined as a set of tuples. Nothing more!
>
> There are several definitions, but that is neither here nor there.
> Relations were chosen because they look and behave a lot like the extensions
> of first order predicates. Of course the extension of a predicate includes
> both positive and negative formulae, but the closed world assumption enables
> the elimination of the negative formulae.

Well I'm not sure what the CWA actually means...

Does the CWA merely relate to the trivial association between a relation (formalised as a set of tuples) and its internal predicate (which is just the relation's boolean-valued characteristic function).

See http://en.wikipedia.org/wiki/Indicator_function

Alternatively does the CWA relate to an assumed association between a relation and an external predicate? If it is the latter then the CWA is clearly outside the RM formalism. Received on Thu Jul 24 2008 - 09:54:14 CDT

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