Re: compound propositions
From: paul c <toledobythesea_at_oohay.ac>
Date: Thu, 18 Mar 2010 21:21:16 GMT
Message-ID: <gPwon.68458$Db2.38232_at_edtnps83>
>
> I, too, find your use of the word sloppy, because a relation is a set of
> things that satisfy a predicate. The relation, itself, doesn't satisfy
> the predicate. Extent or extension is well-defined as a set of instances
> and describes what a relation is: a set of instances that satisfy a
> predicate.
>
> I am not suggesting you never use the word "satisfy". I'm merely
> suggesting more careful use and a different approach when asked for a
> definition.
> ...
Date: Thu, 18 Mar 2010 21:21:16 GMT
Message-ID: <gPwon.68458$Db2.38232_at_edtnps83>
Bob Badour wrote:
> paul c wrote:
>
>> Bob Badour wrote: >> >>> paul c wrote: >>> >>>> Bob Badour wrote: >>>> >>>>> paul c wrote: >>>>> >>>>>> David BL wrote: >>>>>> ... >>>>>> >>>>>>> This boolean valued function can be said to represent a >>>>>>> predicate under an interpretation but I'm not sure if that's what >>>>>>> you >>>>>>> mean. More specifically, what do you mean by "satisfy" when you say >>>>>>> relations satisfy predicates? >>>>>>> ... >>>> >>>> ... >>>> >>>>>> match the variable names apparent in the predicates and the >>>>>> attribute types are applicable for whatever manipulations (eg., >>>>>> aggregation) the predicate states. >>>>> >>>>> In other words, the extension of a predicate is the set of all >>>>> tuples that satisfy the predicate. >>>>> ... >>>> >>>> Yes, but David B asked what 'satisfy' means. >>> >>> In that case, I suggest you not shy away from equality and boolean >>> truth values. Unless you can think of a situation where "satisfy" >>> means something other than "predicate evaluates to true". >> >> I don't know why the fuss about the word 'satisfy'! Admittedly its >> casual but some big names use it from time to time. I certainly >> wasn't trying to alter anybody's vocabulary but I like it because it >> encourages me to distinguish header from value which helps me think >> concretely about implementation. I just don't see the usefulness of >> repetitious acknowledgement that 'it is always true that there is a >> set of featherless bipeds'.
>
> I, too, find your use of the word sloppy, because a relation is a set of
> things that satisfy a predicate. The relation, itself, doesn't satisfy
> the predicate. Extent or extension is well-defined as a set of instances
> and describes what a relation is: a set of instances that satisfy a
> predicate.
>
> I am not suggesting you never use the word "satisfy". I'm merely
> suggesting more careful use and a different approach when asked for a
> definition.
> ...
I didn't give a formal definition and didn't pretend to (my disclaimer was snipped). Received on Thu Mar 18 2010 - 22:21:16 CET