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Re: [RIF-APS] Rules Sign

From: Chris Welty <cawelty@gmail.com>
Date: Tue, 02 Sep 2008 13:50:14 -0400
Message-ID: <48BD7CD6.1060500@gmail.com>
To: kifer@cs.sunysb.edu
CC: Christian de Sainte Marie <csma@ilog.fr>, Jos de Bruijn <debruijn@inf.unibz.it>, Adrian Paschke <adrian.paschke@biotec.tu-dresden.de>, public-rif-wg@w3.org


</chair>
My claim is that every time I see -> *I* think of implication.  This is a basic 
LOGIC dialect, that's what -> means in logic.  This symbol predates C++ by many 
decades, and probably centuries.  I can find out if you really want to belabor it.

-> in C++ was for dereferencing a pointer to a structured object, and was 
supposed to evoke the image of a pointer.  It was shorthand for (*obj).slot  - 
that's not what we're doing here.

As I just said, I'm *not* arguing that -> be used for implication, however.  I 
just don't want the standard implication symbol used for slots and named 
arguments.  It's confusing to anyone familiar with logic.
<chair>

-Chris

Michael Kifer wrote:
> 
> On Tue, 02 Sep 2008 18:45:40 +0200
> Christian de Sainte Marie <csma@ilog.fr> wrote:
> 
>> Michael Kifer wrote:
>>
>>> On Tue, 02 Sep 2008 16:39:36 +0200
>>> Christian de Sainte Marie <csma@ilog.fr> wrote:
>>>
>>>
>>>> Why not use = for frames instead, as in obj[prop = val]?
>>>>
>>>> As I suggested on IRC during last week's telecon, that would reflect the
>>>> semantics that the frame is true iff the value of property 'prop' for object
>>>> 'obj' is equal to 'val'. 
>>>
>>> Such a frame is true NOT if the value is equal to val, but if the value of prop
>>> CONTAINS val.
>> Right. I forgot that. But my point about making it extensible to using other tests than equality remains.
> 
> We can allow extensions that use whatever u want in between name and value.
> This has nothing to do with whether we use -> or hasValue, or whatever.
> 
> B.t.w., the -> is not new and is well established. In this kind of languages it
> goes back almost 25 years to Hasan's Login, or maybe even earlier. I always
> thought that the use of -> comes from C and C++, where -> is used to refer to
> values of properties. And it is also used in SQL in some cases.
> 
> So, Chris' claim that -> always evokes implication is highly subjective.
> It depends who you ask.
> 
> 
> michael
> 

-- 
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty
Received on Tuesday, 2 September 2008 17:50:53 GMT

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