Re: General semantics
From: paul c <toledobythesea_at_oohay.ac>
Date: Wed, 26 May 2010 00:14:27 GMT
Message-ID: <DJZKn.4988$z%6.3629_at_edtnps83>
>
> A reference type has the property of being a (set of all possible)
> reference(s), and nothing more than that.
> A reference (value) has the property of being useful ONLY if a
> dereferencing operator can be applied to it, in order to get to the
> referenced content that actually means something.
> That is the same property that is also a property of pointers.
> And that is why D&D _CORRECTLY_ call them "pointers".
>
>
>
>
> Relations don't record anything. Relation _variables_ do. Speak
> precisely or shut up.
>
>
>
>
> Well, if you do not provide the exact predicate of the relation
> _VARIABLES_ that you have in mind, then it would be pretty hard to
> tell for anyone whether propositions derived from them are synonymous
> or not, no ?
>
>
>
>
> You claim that without giving the precise predicate that you have in
> mind.
>
> If the predicate is "The shop sells product <x> and the current
> quantity available is <y>", then it makes PERFECT SENSE for a tuple
> {"can of cat food", 0} to appear in that relation _VARIABLE_.
>
>
>
Date: Wed, 26 May 2010 00:14:27 GMT
Message-ID: <DJZKn.4988$z%6.3629_at_edtnps83>
Erwin wrote:
> On 25 mei, 23:04, "Mr. Scott" <do_not_re..._at_noone.com> wrote:
>> "paul c" <toledobythe..._at_oohay.ac> wrote in message >> >> news:YodKn.4587$Z6.2983_at_edtnps82... >> >> >> >> >> >>> Mr. Scott wrote: >>> ... >> It is my understanding that an OID is a system-generated name that is >> assigned to an object, and that each OID is assigned to only one object. In >> the OO world, OIDs are only assigned to instances of reference types. Maybe >> that's why D&D erroneously call them pointers.
>
> A reference type has the property of being a (set of all possible)
> reference(s), and nothing more than that.
> A reference (value) has the property of being useful ONLY if a
> dereferencing operator can be applied to it, in order to get to the
> referenced content that actually means something.
> That is the same property that is also a property of pointers.
> And that is why D&D _CORRECTLY_ call them "pointers".
>
>
>
>> Suppose that you have a relation that records what you have in the cupboard,
>
> Relations don't record anything. Relation _variables_ do. Speak
> precisely or shut up.
>
>
>
>> {item, quantity}. >> What is the difference between the following relations (assuming the closed >> world assumption of course)? >> >> {{item:"can of dog food", qty:3},{item:"can of cat food", qty:0}} >> >> {{item:"can of dog food", qty:3}} >> >> 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?
>
> Well, if you do not provide the exact predicate of the relation
> _VARIABLES_ that you have in mind, then it would be pretty hard to
> tell for anyone whether propositions derived from them are synonymous
> or not, no ?
>
>
>
>> Under the closed world assumption, the >> proposition that is the result of substituting the values "can of cat food" >> and 0 for the variables in the predicate for the second relation is supposed >> to be false because the tuple doesn't appear in the relation!
>
> You claim that without giving the precise predicate that you have in
> mind.
>
> If the predicate is "The shop sells product <x> and the current
> quantity available is <y>", then it makes PERFECT SENSE for a tuple
> {"can of cat food", 0} to appear in that relation _VARIABLE_.
>
>
>
Nice answers, thanks. The predicates were indeed missing, but I wanted to add that trying to record 'negative' facts (if that was what the unspoken predicates involved) might lead to contradictions or at the least very tricky interpretations. Received on Wed May 26 2010 - 02:14:27 CEST