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Re: Open world issue (opening vs closing days) and SPARQL CONSTRUCT

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Tue, 20 May 2008 09:38:45 +0200
Message-ID: <48328005.2030704@mondeca.com>
To: staab@uni-koblenz.de
Cc: Adrian Walker <adriandwalker@gmail.com>, semantic-web@w3.org

Steffen, Adrian

Thanks a lot for the useful links. Will try to make sense of all that :)

Bernard

Steffen Staab a écrit :
>
> Hi
>
> SPARQL has an implicit negation, allthough a very crude one using a 
> tricky combination of optional, filter and bound expressions.
> SPARQL also closes the world locally, as described in papers by 
> Polleres or Schenk.
>
> Here is a paper (among others) which describes the negation with an 
> example:
> http://www.uni-koblenz.de/~sschenk/publications/2008/Schenk2008WWW.pdf
>
> And here is an implementation on top of Sesame to do the kind of 
> derivation with SPARQL you are looking for:
> http://www.uni-koblenz.de/FB4/Institutes/IFI/AGStaab/Research/NetworkedGraphs 
>
>
> Cheers,
> Steffen
>
> Adrian Walker schrieb:
>> Hi Bernard & Peter --
>>
>> Some folks regard the lack of an official relational-database-style 
>> negation in SPARQL as a design flaw.  For example, it breaks the 
>> implied analogy with SQL, which does of course have closed world 
>> negation.
>>
>> I'm not a SPARQL expert, but my understanding is that there are 
>> several hacks one can do to get SQL-like negation -- one of them is 
>> to use a SPARQL "filter" keyword.
>>
>> The lack of standardized aggregations in SPARQL is also a worry.
>> The task that Bernard describes would be straightforward to implement 
>> in the deductive system that is online at the site below, mainly 
>> because that system embodies different design choices.
>>
>> Some examples to light the way:
>>
>>    www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent 
>> <http://www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent> 
>>
>>
>>    www.reengineeringllc.com/demo_agents/Calendar1.agent 
>> <http://www.reengineeringllc.com/demo_agents/Calendar1.agent>
>>
>>    
>> www.reengineeringllc.com/demo_agents/Oil-IndustrySupplyChain1MySql1.agent 
>> <http://www.reengineeringllc.com/demo_agents/Oil-IndustrySupplyChain1MySql1.agent> 
>>
>>
>> Hope this helps.
>>
>>                                   -- Adrian
>>
>> Internet Business Logic
>> A Wiki and SOA Endpoint for Executable Open Vocabulary English over SQL
>> Online at www.reengineeringllc.com 
>> <http://www.reengineeringllc.com>    Shared use is _free_
>>
>> Adrian Walker
>> Reengineering
>>   
>>
>>
>>
>> On Mon, May 19, 2008 at 5:38 PM, Peter Ansell <ansell.peter@gmail.com 
>> <mailto:ansell.peter@gmail.com>> wrote:
>>
>>
>>     You might just have to give in and describe either every day as 
>> being
>>     open or closed, especially if you want to use CONSTRUCT against a
>>     known URI, which you wouldn't have in your current system. Maybe the
>>     implicit statements that people accept normally can't actually be
>>     interpreted by a dumb computer system, although with numeric/date
>>     ranges you could easily construct regions where things are open on
>>     concurrent days (although I don't know the specifics about how much
>>     date or numeric reasoning a sparql engine would need to have in this
>>     respect).
>>
>>     Basically I would say that you have to put knowledge in to get
>>     reasoning back, so either you put the knowledge into an ontology 
>> that
>>     any day without "opening" is considered closed, or vice-versa, or 
>> you
>>     describe every possibility as open or closed. Is it that hard in 
>> this
>>     context to be describing both cases?
>>
>>     Peter
>>
>>     2008/5/20 Bernard Vatant <bernard.vatant@mondeca.com
>>     <mailto:bernard.vatant@mondeca.com>>:
>>     >
>>     > Hi all
>>     >
>>     > We're currently fighting with knowledge extraction about
>>     opening/closing
>>     > days for tourism facilities (hotels, restaurants, museums,
>>     campings ...).
>>     > Information can be found in terms of closing and/or opening days
>>     during a
>>     > period, such as :
>>     > "Widget Museum is open in 2008, from March 1st to October 31st,
>>     closed on
>>     > Sunday and Tuesday".
>>     > NLP can extract the following description (1)
>>     >
>>     > :WidgetMuseum   :openingPeriod   _:p1
>>     > _:p1      :begins     2008-03-01
>>     > _:p1      :ends        2008-10-31
>>     > _:p1      :closingDay      :Tuesday
>>     > _:p1      :closingDay      :Sunday
>>     >
>>     > In an open world, we have no way to know if this is a complete
>>     description,
>>     > and can't infer that Widget Museum is open on Monday.
>>     >
>>     > The other way round, if the information is given in terms of
>>     opening days,
>>     > "Widget Museum is open in 2008, from March 1st to October 31st,
>>     on Monday,
>>     > Wednesday, Thursday, Friday and Saturday".
>>     > Which yields the description (2)
>>     >
>>     > :WidgetMuseum   :openingPeriod   _:p2
>>     > _:p2      :begins     2008-03-01
>>     > _:p2      :ends        2008-10-31
>>     > _:p2      :openingDay      :Monday
>>     > _:p2      :openingDay      :Wednesday
>>     > _:p2      :openingDay      :Thursday
>>     > _:p2      :openingDay      :Friday
>>     > _:p2      :openingDay      :Saturday
>>     >
>>     > ... we can't infer that Widget Museum is closed on Tuesday and
>>     Sunday. IOW
>>     > there is no way to identify logically _:p1 and _:p2 in an open
>>     world.
>>     >
>>     > Supposing (1) is the standard target description required by the
>>     ontology
>>     > used in the system, I thought possible to write, in our closed
>>     world, a
>>     > SPARQL CONSTRUCT query which would yield (1) from (2).
>>     > But thinking twice, my hunch is now that it is impossible,
>>     because of the
>>     > implicit open world assumption made by SPARQL.
>>     >
>>     > Has someone already dealt with such issues? Any pointer welcome.
>>     >
>>     > Thanks for your help
>>     >
>>     > Bernard
>>     >
>>     > --
>>     >
>>     > *Bernard Vatant
>>     > *Knowledge Engineering
>>     > ----------------------------------------------------
>>     > *Mondeca**
>>     > *3, cité Nollez 75018 Paris France
>>     > Web:    www.mondeca.com <http://www.mondeca.com>
>>     <http://www.mondeca.com>
>>     > ----------------------------------------------------
>>     > Tel:       +33 (0) 971 488 459
>>     > Mail:     bernard.vatant@mondeca.com
>>     <mailto:bernard.vatant@mondeca.com>
>>     <mailto:bernard.vatant@mondeca.com
>>     <mailto:bernard.vatant@mondeca.com>>
>>     > Blog:    Leçons de Choses <http://mondeca.wordpress.com/>
>>     >
>>     >
>>     >
>>     >
>>
>>
>
>
>

-- 

*Bernard Vatant
*Knowledge Engineering
----------------------------------------------------
*Mondeca**
*3, cité Nollez 75018 Paris France
Web:    www.mondeca.com <http://www.mondeca.com>
----------------------------------------------------
Tel:       +33 (0) 971 488 459
Mail:     bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com>
Blog:    Leçons de Choses <http://mondeca.wordpress.com/>
Received on Tuesday, 20 May 2008 07:39:33 GMT

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