- From: Pierre-Antoine Champin <swlists-040405@champin.net>
- Date: Wed, 21 May 2008 09:03:44 +0200
- CC: Semantic Web <semantic-web@w3.org>
Peter Ansell a écrit : > 2008/5/21 Pierre-Antoine Champin <swlists-040405@champin.net>: >> Bernard Vatant a écrit : >>> 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 >> May be I don't understand your problem well, but it seems to me that there >> is another way of "closing" the world in this particulat context : using a >> *functional* property :closingDays, and have its value be an rdf:List >> collection, which in Turle/SPARQL is written : >> >> :WidgetMuseum :openingPeriod _:p1 >> _:p1 :begins 2008-03-01 >> _:p1 :ends 2008-10-31 >> _:p1 :closingDays (:Tuesday :Sunday) >> >> >> Whether this structure is easy to query with SPARQL, I'm not sure... But it >> seems to me that it makes your knowledge about opening and closing days >> complete. >> > > RDF Collections, including List's are defined to be complete [1], so > that may be one way of getting around the open world assumption, but > how would you imply that a given day was valid and still not in the > closingDays List? Do you have to create another List for openingDays, > which would limit this ability to cases where you know everything? my guess is that the "negation by failure", with the !bound(?u) trick would do it. Informally, a day is valid iff it (as a date) is between :begins and :ends, and it (as a day of week) does not belong to the :closingDays. But once again, I'm not sure how easy it is to formalize that informal query in SPARQL. My point was more about the open/closed world problem... pa
Received on Wednesday, 21 May 2008 07:04:21 UTC