To be able to talk explicitly about a change in an object over time, we assign to it a number of possible, “legal” states. Hence, a state is a situation an object can be at. States and values add expressiveness to OPM. A value is a state of an attribute. As such, it is a specialization of state: Whereas objects can have states, only states of attributes, which are objects that describe other object, are called values. States and values enable modeling change in an object while that object retains its identity. We have been using the terms states and values quite intuitively since the early chapters of this book. If objects and processes are the building blocks of OPM, and links are the mortar, states can be considered as the finish of the house: the paint job, the furniture, and architectural elements. At any time in the life of the object, when no process is acting on it, that object is at one of its states. Cause and effect are tightly linked with the concepts of change of state over time. This chapter formalizes the concepts of states and values, and shows how they can be used to enhance model expressiveness.


State Suppression Structural Link Default State Compound State Path Label 
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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Dov Dori
    • 1
    • 2
  1. 1.Technion, Israel Institute of TechnologyHaifaIsrael
  2. 2.Massachusetts Institute of TechnologyCambridgeUSA

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