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Re: scope of _:existentials in N3Logic?

From: Jakub Kotowski <jakubkotowski@gmx.net>
Date: Sun, 28 Feb 2010 20:44:32 +0100
Message-ID: <4B8AC7A0.2090607@gmx.net>
To: Graham Klyne <GK-lists@ninebynine.org>
CC: jos.deroo@agfa.com, connolly@w3.org, public-cwm-talk@w3.org, public-cwm-talk-request@w3.org
Graham Klyne wrote:
> FWIW, I ran into some similar problems when playing with Swish and
> inference rules - handling bnodes got rather messy.  
Why were bnodes a problem?

> Eventually I
> figured (but didn't get round to implementing) that I could convert to
> some kind of unique generated id on loading the data, and use similar
> when introducing existentials in inferences, 
You mean that you did (or wanted to) generate URIs (instead of bnodes)
when there were existentially quantified variables in the rule heads?

Would it help if the language allowed you to construct URIs for new
resources? I was working on a thing like that for a bit.

Jakub


> treat these like any other
> URI for inference purposes, than convert back to bnodes when saving the
> data.
> 
> #g
> -- 
> 
> jos.deroo@agfa.com wrote:
>>   It took us 10 years to realize that the scope of blank nodes is the
>> graph in which they occur :-)
>> The answer we get from euler is the same as you got from cwm:
>>
>> eye --nope varscope1.n3 --pass
>> #Processed by $Id: euler.yap 3310 2010-02-24 21:31:52Z josd $
>>
>> @prefix : <evarscope1#>.
>> @prefix var: < http://localhost/var# <http://localhost/var#> >.
>> @prefix e: < http://eulersharp.sourceforge.net/2003/03swap/log-rules#
>> <http://eulersharp.sourceforge.net/2003/03swap/log-rules#> >.
>> @prefix r: < http://www.w3.org/2000/10/swap/reason#
>> <http://www.w3.org/2000/10/swap/reason#> >.
>> @prefix n3: < http://www.w3.org/2004/06/rei#
>> <http://www.w3.org/2004/06/rei#> >.
>>
>> :bob :likes _:somebody_1.
>> :fred :likes _:somebody_1.
>> :alice :likes :trina.
>> :trina :likes _:sk0.
>>
>>
>> Kind regards,
>>
>> Jos De Roo | Agfa HealthCare
>> Senior Researcher | HE/Advanced Clinical Applications Research
>> T  +32 3444 7618
>> http://www.agfa.com/w3c/jdroo/ <http://www.agfa.com/w3c/jdroo/>
>>
>> Quadrat NV, Kortrijksesteenweg 157, 9830 Sint-Martens-Latem, Belgium
>> http://www.agfa.com/healthcare <http://www.agfa.com/healthcare>
>>
>>
>> *Dan Connolly <connolly@w3.org>*
>> Sent by: public-cwm-talk-request@w3.org
>>
>> 02/23/2010 11:16 PM
>>
>>     
>> To
>>     public-cwm-talk@w3.org
>> cc
>>     
>> Subject
>>     scope of _:existentials in N3Logic?
>>
>>
>>     
>>
>>
>>
>>
>>
>>
>> I'm re-implementing N3Logic in scala... in particular, parsing
>> N3 syntax into Coherent formulas. I'm trying to figure
>> out how existential variables work in N3, and I'm surprised about
>> something.
>>
>> Consider:
>>
>>  There's somebody that Bob likes and Fred likes.
>>  And everybody that Alice likes also likes this somebody.
>>  Also, Alice likes Trina.
>>
>>  Does Trina like this somebody?
>>
>> Of course Trina does, but when I try to write the problem
>> down in N3, cwm doesn't handle it as I'd expect. cwm concludes
>> that Trina likes something, but not that Trina likes
>> the same somebody that Bob and Fred like.
>>
>> $ cat ...varscope1.n3
>> @prefix : <evarscope1#>.
>> @keywords is, of, a.
>>
>> bob likes _:somebody.
>> fred likes _:somebody.
>> { alice likes ?X } => { ?X likes _:somebody }.
>> alice likes trina.
>>
>> $ cwm.py ...varscope1.n3 --think
>> #Processed by Id: cwm.py,v 1.197 2007/12/13 15:38:39 syosi Exp
>>        #    using base
>> file:///home/connolly/projects/rdfsem/src/test/resources/varscope1.n3
>> <file:///home/connolly/projects/rdfsem/src/test/resources/varscope1.n3>
>>        #  Notation3 generation by
>> #       notation3.py,v 1.200 2007/12/11 21:18:08 syosi Exp
>>
>> #   Base was:
>> file:///home/connolly/projects/rdfsem/src/test/resources/varscope1.n3
>> <file:///home/connolly/projects/rdfsem/src/test/resources/varscope1.n3>
>>     @prefix : <evarscope1#> .
>>    @prefix va: <#> .
>>        @forAll va:X.
>>         @forSome va:_g0 .
>>       :alice     :likes :trina .
>>       :bob     :likes va:_g0 .
>>       :fred     :likes va:_g0 .
>>       :trina     :likes  [
>>         ] .
>>    {
>>        :alice     :likes va:X .
>>               }     < http://www.w3.org/2000/10/swap/log#implies
>> <http://www.w3.org/2000/10/swap/log#implies> >
>> {va:X     :likes  [
>>             ] .
>>        } .
>>    #ENDS
>>
>> The surprise is bad news, but the good news is that cwm's
>> way of reading this formula does fit inside coherent logic,
>> which makes my coding goal straightforward...
>>
>> -- 
>> Dan Connolly, W3C http://www.w3.org/People/Connolly/
>> <http://www.w3.org/People/Connolly/>
>> gpg D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
>>
>>
>>
>>
> 
> 
> 
Received on Sunday, 28 February 2010 19:45:38 GMT

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