A subclass of Service(W,P,E,Provider,Caller,I,O,D)
Where D is a machine-readable, accessible description
of a particular service with a variable for the
Caller, and the values of the propositions
in P,E,I,O, and
explicit descriptions of how and where the sent
and received signals should be sent, which
designates an instantiation of the Provider.
The variables inP,I must be instantiated
in the state in which the service is requested.
The variables of E,O are instantiated
after the performance of the service. Some value variables
may not be instantiated.
Special formulation: the object of each proposition
in the conditions may nil.
Example: Color(nil Blue).
This may be designated in Inputs and Outputs as simple
assignments of values to properties: p:=v.
For this reason, the Inputs and Outputs may be designated
as simple vectors of properties:
