The Structural System Aspect
Structure pertains to the relatively fixed, non-transient, long-term relationships that exist among objects—components or parts of the system. Alternatively, structure can be viewed as a snapshot—a picture of the generally dynamic system, or part of it, at some point in time. This snapshot captures the entire system at some state, where each stateful object is at some state or in transition between two of its states, and specific relationships between objects hold. Structure is contrasted with the complementary dynamic aspect of the system, or its behavior, which has to do with the changes the system undergoes over time, along with the causes for and effects of these changes. In other words, structure is about the static aspect of the system, while behavior is about its dynamic aspect. This chapter is devoted to discussing the structure of systems and expressing it through OPM.