Re: General semantics

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...
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>
>
>
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> > Mr. Scott wrote:
> > ...
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> 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}}
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> {{item:"can of dog food", qty:3}}
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> 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_. Received on Wed May 26 2010 - 00:57:15 CEST