Re: General semantics

"Erwin" <e.smout_at_myonline.be> wrote in message news:566b6ba2-592b-4b62-8e4a-30805a7c72fb_at_j9g2000vbp.googlegroups.com...
> On 26 mei, 03:46, "Mr. Scott" <do_not_re..._at_noone.com> wrote:
>> "Erwin" <e.sm..._at_myonline.be> wrote in message
>>
>> news:4df4d884-e6bb-427e-b97b-96647f171a11_at_m33g2000vbi.googlegroups.com...
>> On 25 mei, 23:04, "Mr. Scott" <do_not_re..._at_noone.com> wrote:
>>
>>
>>
>>
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>> > "paul c" <toledobythe..._at_oohay.ac> wrote in message
>>
>> >news:YodKn.4587$Z6.2983_at_edtnps82...
>>
>>
>>
>
>> A relation is what has been recorded, so there is nothing wrong with
>> referring to what it records.
>
> Interpreting the meaning of a relation can only be done when some
> predicate is given to do that interpreting. Predicates are tied to
> relation _variables_, not to relations. TABLE_DEE appearing as the
> value for relvar THE_SHOP_IS_OPEN means something different than
> TABLE_DEE appearing as the value for relvar THE_ALARM_IS_SET.
>
> Saying that relations have meaning irrespective of some predicate
> coming from some relvar, is a plain and simple admission of the fact
> that you simply aren't getting it.
>

I didn't say anything about meaning. The predicate of the relation that mentions cans of cat food is identical to the predicate of the relation that doesn't. Under the closed world assumption, the FORM of the resultant proposition for each given relation is different--regardless of what the predicate means. Let me put it another way:

(Pab /\ Pcd /\ ~Pad /\ ~Pcb) /\ (Pab /\ ~Pad /\ ~Pcb /\ ~Pcd)

is LOGICALLY false. There is no need to analyze (assign meaning) because no matter what P ultimately means, the expression is still false!

>
>> > Both indicate that there are three cans of dog food, but does the
>> > second
>> > indicate that there is no such thing as a can of cat food, or is it
>> > synonymous with the first?
>
> It depends on the predicate of the relvar that these relations might
> appear for.

No, it doesn't!

<snip>

> .... My understanding is that
> you are trying to turn this into a deficiency of the relational
> model. It is not. It is just a property of the number zero, and it
> is just the logical meaning of any quantity being zero.

It is not the relational model that is deficient. The problem is that quantities like the number of cans of cat food are in essence aggregate values, and there are consequences to recording aggregate values in base relations. I'm not saying it is necessarily wrong to do so, but I will say that it is wrong to treat the absence of tuples with zero quantity as if they were indeed present. That's just plain sloppy.

<snip> Received on Wed May 26 2010 - 16:05:49 CEST