- From: Bernard Vatant <bernard.vatant@mondeca.com>
- Date: Tue, 20 May 2008 09:36:45 +0200
- To: Peter Ansell <ansell.peter@gmail.com>
- Cc: Semantic Web <semantic-web@w3.org>
Hi Peter Thanks for your quick and helpful answer. What I understand from it is that we have to build the closed world assumptions in the ontology rather than in constructive rules, such as define a "SundayClosed" class with "hasValue Sunday" restriction on "closingDay" property, and a matching "SundayOpen" class, declare them as complement of each other subclasses of "Opening". We did not want to go through such a complexity in the ontology to begin with, since actually the time granularity we want to handle is finer than "day", with fuzzy things like morning, afternoon, and evening. Before coming back to such an extreme solution, we will look at SPARQL stuff proposed by Stefen and Adrian Bernard Peter Ansell a écrit : > 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>: > >> 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> >> ---------------------------------------------------- >> Tel: +33 (0) 971 488 459 >> Mail: 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 07:37:27 UTC