Dynamic Diagrams

The diagrams in this chapter allow you to model the dynamic behavior of your system, how its objects interact at run-time. PowerDesigner provides four types of diagrams for modeling your system in this way:

• Communication Diagrams
  A communication diagram is a UML diagram that provides a graphical view of the interactions between objects for a use case scenario, the execution of an operation, or an interaction between classes, with an emphasis on the system structure.
• Sequence Diagrams
  A sequence diagram is a UML diagram that provides a graphical view of the chronology of the exchange of messages between objects and actors for a use case, the execution of an operation, or an interaction between classes, with an emphasis on their chronology.
• Activity Diagrams
  An activity diagram is a UML diagram that provides a graphical view of a system behavior, and helps you functionally decompose it in order to analyze how it will be implemented.
• Statechart Diagrams
  A statechart diagram is a UML diagram that provides a graphical view of a State Machine, the public behavior of a classifier (component or class), in the form of the changes over time of the state of the classifier and of the events that permit the transition from one state to another.
• Interaction Overview Diagrams
  An interaction diagram is a UML diagram that provides a high-level graphical view of the control flow of your system as it is decomposed into sequence and other interaction diagrams.
• Messages (OOM)
  A message is a communication between objects. The receipt of a message will normally have an outcome.
• Activations (OOM)
  Activations are optional symbols that represent the time required for an action to be performed. They are created on the lifeline of an object. They are purely symbols and do not have property sheets.
• Interaction References and Interaction Activities (OOM)
  An interaction reference is used to represent one sequence diagram in the body of another. This feature allows you to modularize and reuse commonly-used interactions across a range of sequence diagrams. Interaction activities are similar, but are able to represent a sequence, communication, or interaction overview diagram.
• Interaction Fragments (OOM)
  An interaction fragment allows you to group related messages in a sequence diagram. Various predefined fragment types are available allowing you to specify alternate outcomes, parallel messages, or looping.
• Activities (OOM)
  An activity is the invocation of a manual or automated action, such as "send a mail", or "increment a counter". When the activity gains control, it performs its action and then, depending on the result of the action, the transition (control flow) is passed to another activity.
• Organization Units (OOM )
  An organization unit can represent a company, a system, a service, an organization, a user or a role, which is responsible for an activity. In UML, an organization unit is called a swimlane, while in the OOM, "swimlane" refers to the symbol of the organization unit.
• Starts and Ends ( OOM)
  A start is a starting point of the flow represented in the diagram, and an end is a termination point of the flow.
• Decisions ( OOM)
  A decision specifies which path to take, when several paths are possible. A decision can have one or more input flows and one or more output flows, each labeled with a distinct guard condition, which must be satisfied for its associated flow to execute some action. Your guard conditions should avoid ambiguity by not overlapping, yet should also cover all possibilities in order to avoid process freeze.
• Synchronizations ( OOM)
  A synchronization enables the splitting or synchronization of control between two or more concurrent actions.
• Flows ( OOM)
  A flow is a route the control flow takes between objects . The routing of the control flow is made using guard conditions defined on flows. If the condition is true, the control is passed to the next object.
• Object Nodes (OOM)
  An object node is the association of an object (instance of a class) and a state. It represents an object in a particular state.
• States (OOM)
  A state represents a situation during the life of a classifier that is usually specified by conditions. It can also be defined as the situation of a classifier waiting for events. Stability and duration are two characteristics of a state.
• Transitions (OOM)
  A transition is an oriented link between states, which indicates that an element in one state can enter another state when an event occurs (and, optionally, if a guard condition is satisfied). The expression commonly used in this case is that a transition is fired.
• Events (OOM)
  An event is the occurrence of something observable. The occurrence is assumed to be instantaneous and should not have duration.
• Actions (OOM)
  An action is a specification of a computable statement. It occurs in a specific situation and may comprise predefined events (entry, do and exit) and internal transitions.
• Junction Points (OOM)
  A junction point can merge and/or split several input and output transitions. It is similar to the decision in the activity diagram