Re: RM formalism supporting partial information
Date: Wed, 28 Nov 2007 05:54:24 -0800 (PST)
Message-ID: <51ba7325-a9f0-4435-9b5e-bdf0c945737f_at_i29g2000prf.googlegroups.com>
On 28 nov, 14:24, paul c <toledobythe..._at_ooyah.ac> wrote:
> Jan Hidders wrote:
> > On 28 nov, 01:58, David BL <davi..._at_iinet.net.au> wrote:
> ...
> >> Consider a query to find all the 27 year old pilots from a census
> >> recorded in an RDB. If the age or occupation is missing we could
> >> think of the person as a possible answer.
>
> > I believe there is a terminology problem here concerning the terms
> > "possible answers" and "certain answers". In the context of research
> > on incomplete databases (i.e. anywhere the classical CWA does not
> > apply fully) that usually means the following. Given a query and the
> > assumptions about "closedness" the set all tuples with the right
> > header can be partitioned into three groups: the certain answers
> > (those that are certain to be in the result of the query on the
> > omniscient database), the possible answers (those that might be in the
> > aforementioned result) and the impossible answers (those that are
> > certain not to be in the aforementioned result).
>
> > In that sense the tuple describing the person you mentioned above
> > (presuming it is projected on the non-null fields) is a certain
> > answer, not a possible answer.
> > ...
>
> When it comes to a public census I believe the possible answers or
> non-answers are planned for.
- Jan Hidders