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6.3.4 Semantics Descriptions in the Specification

   The general causality model is described in the introductory part of Chapter 13 (CommonBehaviors) and also, in part, in the introduction to Chapter 14 (Interactions) and the section on Interaction (14.3.13) and Message (14.3.20).

   The structural foundations are mostly covered in two chapters. The elementary level is mostly covered in Chapter 7, where the root concepts of UML are specified. In particular, the sections on InstanceSpecifications (7.3.22), Classes (7.3.7) Associations (7.3.3), and Features (7.3.19). The composites level is described primarily in Chapter 9 (Composite Structures), with most of the information related to semantics contained in sections 9.3.12 (Property concept) and 9.3.13 (StructuredClassifier ). In addition, the introduction to this chapter contains a high-level view of some aspects of composite structures.

   The relationship between structure and behavior and the general properties of the Behavior concept, which are at the core of the behavioral base are described in CommonBehaviors (in the introduction to Chapter 13 and in section 13.3.2 in particular).

   Inter-object behavior is covered in three separate chapters. The basic semantics of communications actions are described in the introduction to Chapter F (Actions) and, in more detail, in the sections describing the specific actions. These can potentially be used by an object on itself, so can be inter- or intra-object. The read/write actions can also be used by one object to access other objects, so are potentially inter- or intra-object. These actions can be used by any of the behavior formalisms in UML, so all are potentially inter-object behaviors. However, the interactions diagram is designed specifically to highlight inter-object behavior, under its concept of message. These are defined in the Interactions chapter (sections 14.3.20 and 14.3.21), while the concepts of events and triggers are defined in the Communications package of CommonBehaviors (Chapter 13). Occurrence specifications are defined in section 14.3.25 of the Interactions chapter. The other two behavior formalisms can be translated to interactions when they use inter-object actions.

   All the behavior formalisms are potentially intra-object, if they are specified to be executed by and access only one object. However, state machines are designed specifically to model the state of a single object and respond to events arriving at that object. Activities can be used in a similar way, but also highlight input and output dependency between behaviors, which may reside in multiple objects. Interactions are potentially intra-object, but generally not designed for that purpose.

   The various shared actions and their semantics are described in Chapter 13.

   Finally, the higher-level behavioral formalisms are each described in their own chapters: Activities in Chapter 12, Interactions in Chapter 14, and State Machines in Chapter 15.