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Re: Modeling complex results as logic formulas, or as composite proce sses

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Thu, 16 Dec 2004 14:43:17 -0500
Message-ID: <16833.58709.517132.111138@dhcp130132249245.its.yale.edu>
To: "Camara Melgosa, Javier" <JCAMARA@softwareag.es>
Cc: public-sws-ig@w3.org

> [Javier Camara]
> I have an scenario in which want to find out whether a person is working at
> a given date and time, i.e. isWorking(Person,Time) . There are two available
> services for performing this, one telling me whether isWorkingTime(Time) and
> other telling whether isOnHoliday(Person,Date). Thus, one can say that
>         isWorking(Person,Time) == isWorkingTime(Time) & not
> isOnHoliday(Person,Date(Time) )
> Now, how would it be better to model this in OWL-S? Assuming the existing
> services have OWL-S descriptions including no effect and with respective
> outputs of isWorkingTime(Time) and isOnHoliday(Person,Date), I can see at
> least three options:
> 1) In the requester profile,specify a required output of
> isWorking(Person,Time) , and then define using OWL that
> isWorking(Person,Time) is equivalent to isWorkingTime(Time) & not
> isOnHoliday(Person,Date(Time) )
> 2) In the requester profile, directly specify a required output of
> isWorkingTime(Time) & not isOnHoliday(Person,Date(Time) )
> 3) Have the requester profile specifying an output of
> isWorking(Person,Time), and create a new composite process description whose
> output is isWorking(Person,Time) and whose model invokes the two existing
> services in a proper way
> I would choose option 1) , but it looks to me that most OWL-S processors
> would handle better option 3). Any opinion on this? Would option would be
> better? Are there other options?

I like option (1) as well, although I would try to be a bit more
precise in specifying the outputs and effects.  What is requested is a
service such that invoking it will produce a boolean-literal output B
with effect "knows-value-is(client, isWorking(Person,Time), B)."
However, that doesn't address your main question.

I don't think an Owl-S processor's job is to figure out how to achieve
the requested goal.  You need a planner with a reasoning engine clever
enough to infer that if P & Q <-> R, then one way to achieve 
KG = knows-value(client, R) is to achieve 

        knows-value-is(client,P,true) & knows-value-is(client,Q, true)

(omitting several important details).  If we schematize this as 

       KG = ((KG1 & KG2) OR KG3 OR KG4)

then the planner must figure out that service 1 will achieve KG1 or
KG3, and service 2 will achieve KG2 or KG4, after which it will have
achieved KG.


                                         -- Drew McDermott
                                            Yale University
                                            Computer Science Department
Received on Thursday, 16 December 2004 19:42:25 UTC

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