Re: compound propositions

From: paul c <>
Date: Thu, 18 Mar 2010 18:59:03 GMT
Message-ID: <XJuon.68456$Db2.62487_at_edtnps83>

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'. Received on Thu Mar 18 2010 - 19:59:03 CET

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