A structure-function modeling paradigm for engineering databases

摘要

A unifying data representation paradigm is proposed for modeling and integrating engineering systems. This paradigm, called the structure-function paradigm, consists of structural information, functional information, and interactions between structures and functions. Structural information models the physical system, physical constraints, and the system state, whereas functional information models the overall behavior of the system. Well-defined interactions model the many-to-many semantic associations between the structural and the functional information. The structure-function paradigm uses object-oriented concepts where the structures are represented by structural objects, the functions are represented by functional objects, and the interactions between structures and functions are represented by interaction objects. This paradigm is based on the premise that structural and functional models of inherently complex natural and man-made systems are not isomorphic, i.e., the abstractions in the structural domain do not correspond to abstractions in the functional domain, and vice versa. Moreover, a function is carried out by many structures with possible alternate options; in addition, a structure will support many functions, also with alternatives. Therefore, structures and functions are represented and abstracted independently by structural object hierarchies and by functional object hierarchies, respectively, and the relationship between these hierarchies are modeled by interaction objects. These hierarchies are further extended to directed acyclic graphs. Invariants ensure that the structural objects and the functional objects are abstracted correctly. A set of rules for preserving the integrity and correctness of composite structural objects and composite functional objects are presented. The proposed representation also supports an active database environment by modeling events which monitor input data and system state, and initiate and terminate actions. These events trigger a set of constraints to ensure the consistency of the system representation, thus making this paradigm suitable for monitoring and simulating applications. The utility of this paradigm is demonstrated in two areas--discrete manufacturing and computer integrated manufacturing. In discrete manufacturing, the structure-function paradigm helps the designer in making design choices for building robotic workcells. In computer integrated manufacturing, the structure-function paradigm is used to integrate engineering databases with operational information such as application packages into one integrated environment.