Re: compound propositions
Date: Thu, 18 Mar 2010 18:59:03 GMT
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