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

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

   www.reengineeringllc.com/demo_agents/Calendar1.agent

   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    Shared use is *free*

Adrian Walker
Reengineering





On Mon, May 19, 2008 at 5:38 PM, Peter Ansell <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>:
> >
> > 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/>
> >
> >
> >
> >
>
>