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Re: [ontolog-forum] language vs logic - ambiguity and starting with defi

 To: "[ontolog-forum]" Christopher Menzel Tue, 21 Sep 2010 20:34:39 -0500 <1EFD427B-E38E-4105-9185-F135471E2A61@xxxxxxxx>
 ```On 9/21/2010 6:08 PM, Jerry Hobbs wrote: > Chris, > > I was rather surprised to see you criticizing Ernie Davis, since he is > probably the best there is in formalizing commonsense knowledge. His > 1990 book "Representations of Commonsense Knowledge" is still probably > the best introduction to the field. > > So I checked out the 6-page note cited. It is limited in ambition -- > it is only a list of common student errors, presumably for use by his > students. But I didn't see where it is wrong. I'm curious about what > mistakes you found.    (01) Hi Jerry,    (02) No doubt I'm overly snooty about such things (and I'm certainly glad to hear someone of your stature vouching for the quality of his work), but several features put me off right away:    (03) 1. The use of upper case letters for first-order variables. The usual convention among logicians is to reserve upper case letters for second-order variables.    (04) 2. Constructing the quantifiers by tacking the bound variable on as a *subscript* to the quantifier. Why? I know of no commonly used text that adopts this convention.    (05) 3. The more serious issue: unconventional quantifier scoping. On the first page, Davis translates "Same has a male child" as:    (06) (1.3) ∃X child(X,sam) ∧ male(X)    (07) So the scope of the quantifier here is obviously supposed to be the entire formula "child(X,sam) ∧ male(X)" to its right. But according to the grammar found in most any modern text, (1.3) is a conjunction formed from "∃X child(X,sam)" and "male(X)"; the occurrence of X in the latter formula is simply free -- a perfectly acceptable formula in a basic, context-free first-order language. To get the intended scope, you need appropriate delimiters:    (08) (1.3a) ∃X [child(X,sam) ∧ male(X)]    (09) I guess Davis's convention is to give quantifiers the widest possible scope unless delimiters indicate otherwise, as in his example:    (010) (7.3) ∀X [∃Y meat(Y) ∧ eats(X,Y)] ⟺ ¬vegetarian(X).    (011) And perhaps that is the way it's done by a lot of folks in the commonsense realm. But it certainly seems to me to be out of step with standard practice amongst most logicians and philosophers. I'm sure Davis's syntax can be made rigorous but, even aside from its unconventional qualities, it seems to me it would be awkward to state the truth definition for the language. (Perhaps the best way to do it would be to have a more standard formal syntax where (1.3a) would be strictly correct and (1.3) would be acceptable via certain parenthesis dropping conventions.)    (012) Regards,    (013) -chris    (014) _________________________________________________________________ Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/ Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/ Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx Shared Files: http://ontolog.cim3.net/file/ Community Wiki: http://ontolog.cim3.net/wiki/ To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (015) ```
 Current Thread Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, (continued) Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, Pavithra Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, John F. Sowa Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, Pavithra Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, doug foxvog Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, Christopher Menzel Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, Alex Shkotin Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, Pavithra Re: [ontolog-forum] language vs logic - ambiguity and starting with definitions, Christopher Menzel Re: [ontolog-forum] language vs logic - ambiguity and starting with definitions, Pavithra Re: [ontolog-forum] language vs logic - ambiguity and starting with definitions, Jerry Hobbs Re: [ontolog-forum] language vs logic - ambiguity and starting with definitions, Christopher Menzel <= Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, FERENC KOVACS Re: [ontolog-forum] language vs logic - ambiguity and startingwithdefinitions, FERENC KOVACS