- From: Bernard Vatant <bernard.vatant@mondeca.com>
- Date: Tue, 20 May 2008 09:38:45 +0200
- 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 UTC