ISO 15926-2 states, in 184.108.40.206 , that:
NOTE 2 Specifications or descriptions of useful objects are often intersections of several arrangement classes, allowing both shape and material aspects to be constrained. In this part of ISO 15926, such intersections are members of:
Note that ClassOfFunctionalObject is not in above list, meaning that this class may not be declared as "useful object" such as in the context of a facility.
ISO 15926-2 states for class_of_functional_object, in 220.127.116.11 , that:
A class_of_functional_object is a class_of_arranged_individual that indicates the function or purpose of an object.
EXAMPLE Pump, valve, and car are examples of class_of_functional_object. Particular models of pump, valve, car, etc are instances of class_of_inanimate_physical_object that are specializations of these instances of class_of_functional_object.
This means that DYNAMIC PUMP (rdl:RDS432584) is:
Specializations of core instances of ClassOfFunctionalObject are possible, but require caution. Assume the instance of ClassOfFunctionalObject WHEEL. A specialization could be RIGHT FRONT WHEEL (of a car). In its context that could be a useful subclass.
But a specialization of PUMP to BOILER FEEDWATER PUMP as an instance of ClassOfFunctionalObject causes an unmanageable functional universe in parallel with the physical universe.
Functional modeling, such as process design, control systems design, etc., is not only a matter of functional objects but also of activity modeling, where instances of ClassOfFunctionalObject and of ClassOfStream, participate.