Re: NULLs

From: David BL <davidbl_at_iinet.net.au>
Date: Wed, 2 Jan 2008 16:49:25 -0800 (PST)
Message-ID: <e4ec7b7f-ad6e-4650-aa46-c655b7cd12f6_at_h11g2000prf.googlegroups.com>


On Dec 30 2007, 12:00 am, JOG <j..._at_cs.nott.ac.uk> wrote:
> On Dec 28, 10:59 pm, Hugo Kornelis

> > I doubt it. Given this information:
>
> > * "Employee Jack is male"
> > * "Employee Mary is female"
> > * "Employee Jack is 43 years old"
> > * "Employee JJ is 32 years old"
>
> > how would you answer the below questions:
>
> > * "List all employees aged 40 and above".
> > * "What is the average age of our employees?"
> > * "For each employee, how many years left until retirement (assume a
> > country with laws for retirement age of 65)"
> > * "List all employees that are female, under 35 years old, or both"
> > * "Is JJ older than Mary?"
> > * etc
>
> Yup, I catch your drift. However I believe these questions should have
> "in propositions that you know" concatenated to them, so we still have
> 2VL, and leaving us humans in the real world to interpret the results.
> The CWA is a nonsense imo. But I do agree that with CWA, in RM, 3VL is
> very difficult to avoid, and nulls are incredibly tempting to use. My
> personal conclusion therefore is that perhaps we are trying to
> address /symptoms/ and not the root cause of the issue, and a step
> back is required.

It seems to me that it's the OWA that invites 3VL. I'm thinking that the CWA simply means that an extension is uniquely defined given the intension and when intensional definitions are stated properly 2VL applies.

I think OWA means a recorded extension may only be a subset of the actual extension corresponding to the stated intension, because OWA asserts that a system's knowledge is incomplete. It is the OWA that forces the logical inference system to deal with partial information.

Have I got it wrong? Received on Thu Jan 03 2008 - 01:49:25 CET

Original text of this message