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

From: Peter Ansell <ansell.peter@gmail.com>
Date: Tue, 20 May 2008 07:38:07 +1000
Message-ID: <a1be7e0e0805191438pab3273awa7b538eeb6625967@mail.gmail.com>
To: "Bernard Vatant" <bernard.vatant@mondeca.com>
Cc: "Semantic Web" <semantic-web@w3.org>, "Florence Amardeilh" <florence.amardeilh@mondeca.com>, Steph <steph.weiser@gmail.com>, "Philippe Laublet" <Philippe.Laublet@paris4.sorbonne.fr>

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, citÚ 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>
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>
>
>
>
Received on Monday, 19 May 2008 21:38:46 GMT

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