W3C home > Mailing lists > Public > semantic-web@w3.org > May 2008

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

From: Steffen Staab <staab@uni-koblenz.de>
Date: Tue, 20 May 2008 09:03:00 +0200
Message-ID: <483277A4.8060503@uni-koblenz.de>
To: Adrian Walker <adriandwalker@gmail.com>
CC: semantic-web@w3.org, florence.amardeilh@mondeca.com, steph.weiser@gmail.com, Philippe.Laublet@paris4.sorbonne.fr

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, citÚ 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:    Lešons de Choses <http://mondeca.wordpress.com/>
>     >
>     >
>     >
>     >
>
>
Received on Tuesday, 20 May 2008 07:03:46 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 21:45:22 GMT