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

Hi all - I hope this one is a short question:
 
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?
 
Thanks
--
Javier Cámara (jcamara@softwareag.es <mailto:jcamara@softwareag.es> )
Software Architect, Software AG España, S.A.
Ronda de la Luna, 22; 28760 Tres Cantos (Spain)
+34 91 807 9400, fax +34 91 807 9447