Operations of Functionality

A framework to represent and operate functions is needed, because functions are crucial in various engineering activities. This paper formalizes combining multiple functions . The presented method is based on the Function-Behavior-State (FBS) modeling. In the FBS modeling . a functional world consisting of subjective descriptions and a physical world described based on Qualitative Process Theory are linked with each other . A computer tool named the FBS modeler is extended to handle combination of functiou operations . To represent a function . introdiced are parametric conditions for a function to start or terminate . and subjects of a function . To represent relations among functions . introduced are temporal and structural/spatial relations among functions . To reason about a combination of functions, representations in the functional world are interpreted in the physical world and the behavior simulation is executed. From the results which may include additional physical phenomena . a function is extracted . An example of combining two functions is demonstrated . Importantly . the proposed method guarantees physical soundness .