[Top] [All Lists]

Re: [ontolog-forum] Ontology, Information Models and the 'Real World'

To: Pat Hayes <phayes@xxxxxxx>
Cc: Ontolog Forum <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Waclaw Kusnierczyk <Waclaw.Marcin.Kusnierczyk@xxxxxxxxxxx>
Date: Mon, 16 Apr 2007 23:48:01 +0200
Message-id: <4623EF11.8040906@xxxxxxxxxxx>

Pat Hayes wrote:    (01)

>> Not necessarily a quantifier.  Perhaps mislead by the syntactic 
>> similarity of IKL (and KIF, for that matter), I was thinking in terms 
>> of LISP (Scheme, for that matter).  Then, a syntactic binder is not 
>> necessarily a quantifier, as in a do-loop, it can be a lambda 
>> expression, or the syntactic sugar let:
>> (let ((x 1))
>>   (= (tnb 'x') x))
>> (let ((x 2))
>>   (= (tnb 'x') x))
>> => true
>> => true
>> though 'x' does not denote the same object in the whole scope.
> That is what I meant, yes. But in normal assertional logic, the 
> quantifiers are the only such name-binding operators. Of course all 
> these languages can be rendered down into functors applied to a single 
> binder, usually lambda.
> BUt contexts in context logic play a rather different role: in 
> particular, there is no explicit name binding syntax, only the notion 
> that a name may (or may not) denote differently when asserted relative 
> to a context. Contextual assertion is more like inclusion inside a modal 
> operator than being in a syntactic binding scope.    (02)

Then this is not what I meant.    (03)

>> You can have referential transparence with lexical scoping.  The point 
>> is not to have dynamic scoping.  A purely functional language is 
>> referentially transparent, though names have meanings dependent on the 
>> context (the environment).
> Free names do not, though. In context logic, even free names may change 
> their contextual referents.    (04)

something like:    (05)

(context-let ((x 1 ctx))
   (= (tnb x ctx) 1)
   (= (tnb x ctx) 2))    (06)

=> possibly
=> unsure    (07)

?    (08)

>> Apparently in IKL contexts are whatever one wishes them to be.  I 
>> guess my dog might be a context in IKL, it seems.  Do you have any 
>> definition of context there?
> No definition, no. Following McCarthy, we say that context is whatever 
> satisfies ones axioms which purport to describe contexts. Yes, your dog 
> could be a context, for example for a learned discussion between two 
> veterinary surgeons, where one says "the liver appears to be inflamed" , 
> meaning (but without explicitly saying) the liver *of this dog we are 
> looking at*. McCarthys example is a surgeon saying to his assistant, 
> "scalpel", with the contextual meaning, "Pass me the scalpel that I need 
> at this point, by putting it, handle first, into my outstretched hand."    (09)

He.  I like this metaphore;  I have paritcipated in many surgical 
interventions, and must say that the code surgeons use for communication 
is extremely compact.    (010)

Anaesthesiologists say that the sheet that is placed over the patient's 
neck (between the side of his head and the side of the rest of his body) 
is a blood-brain barrier.  If you have ever seen a major surgery and 
have some hint about physiology, you will get the joke.    (011)

>> OK.  Then what does (tnb s) actually mean?
> Remember s is a character string. It means, whatever that string would 
> denote, if you were to use it as a name. In fact, the 'tnb' is 
> unnecessary: it is sufficient to simply call the string as a function 
> with no arguments: (s)    (012)

Cool trick.  So ('x') and x are semantically equivalent?  And if you do 
not have contexts, what is the purpose of the (tnb s) form -- it seems 
just redundant.    (013)

>>  And what does (tnb s x) actually mean?
> That has no predefined logical meaning, but you can use the form to 
> assign a meaning to it by writing appropriate axioms. You have to do 
> this for contextual meanings anyway: there is no *logical* reason why 
> they should mean anything in particular or that it should be related in 
> any systematic way to their simple (non-contextual) meaning.
>>   (I guess I'd better consult the documentation.)
> http://www.ihmc.us:16080/users/phayes/IKL/GUIDE/guide.html    (014)

yep, thanx.    (015)

> Pat    (016)

Wacek Kusnierczyk    (017)

Department of Information and Computer Science (IDI)
Norwegian University of Science and Technology (NTNU)
Sem Saelandsv. 7-9
7027 Trondheim
Norway    (018)

tel.   0047 73591875
fax    0047 73594466
------------------------------------------------------    (019)

Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/  
Subscribe/Config: 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 Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (020)

<Prev in Thread] Current Thread [Next in Thread>