Activity diagram of UML9 map

Activity diagram is one of the 5 dynamic modeling mechanisms of UML, is a process-oriented description, and describes the workflow of business use case implementation. The activity diagram is also a special example of the state machine, emphasizing the sequence and concurrency steps in the calculation process, where most of the state is active, and most of the transitions are triggered by the completion of the activity in the original state: that is, the effect on the next activity that results from the completion of the previous activity.

an activity diagram is a model view that describes the behavior of a system, which describes the results of actions and actions that result in changes in the state of an object, regardless of the event in which the status changes are issued. Activity diagrams typically document the logic of a single action or method, and the logical flow of use cases. The activity diagram is one of the state diagrams, so the symbol of the activity diagram is similar to the symbol of the state diagram. The start and end of an activity diagram is similar to a state diagram, beginning with a solid circle, and ending with a circle outside a solid circle. In contrast to states in a state diagram, the representation of an activity in an activity diagram is a rectangle close to the ellipse, which is intended to describe the result of changes in the action and the object, without any triggering events.

The role of activity diagrams

1. Describe the work done during the execution of an operation, explaining how the object works.

2. It is particularly useful for use case descriptions that illustrate how instances of use cases perform actions and how to change the state of an object.

3. Shows how to perform a set of related actions, and how those actions affect related items around the object.

4. You can identify how business process operations are performed, and what changes are possible.

5. Algorithms that describe complex processes.

Composition of the activity diagram

Action state: In UML, the action state is represented by an approximate ellipse, which represents a very short event processing time. The action state does not include event-triggered transformations, which are often used to model the steps in the process of workflow execution. Another action state is an atomic action or execution state of an operation, that is, the action is either not executed or fully executed.

Active state: The active state is non-atomic and is used to represent the execution of a purely computed structure with a substructure. The active state can be decomposed into other sub-activities or action states, which can break the transition away from the state, and can have internal transformations, entry actions, and exit actions. Activity state is used to describe the calculation of continuous events or complexities, with long activity times relative to the action state. The two represent the same shape, the difference is that the active state can be in the icon to give the entrance action and exit action and other information.

Combined activity: A composite activity is an inline activity diagram state, nested with several activities or actions that can represent successive, complex, multi-state activities.

Bifurcation and combination: for some large and complex systems, objects often run with more than one control flow, but multiple control flows run concurrently, and in order to better deal with concurrent operations, forks and combinations are introduced in UML. The fork is represented by a bold black line with one input multiple outputs, and the combination is also used in bold black line, which is a output with multiple inputs.

Branching and merging: branching is common in activity diagrams, which is part of the transformation, dividing the transformation path into multiple parts, each with its own guardianship conditions and different results. The most common is the process used to make judgments. A hollow diamond in UML is used to denote judgment, and the activity is divided into two parts after judging. Merging is the opposite of branching, and the most common is when you merge to the same result after judgment, which is merging.

Swimlane: In order to organize the functions of an activity in the activity diagram, the state of a static activity is divided into different groups, which is a swimlane, each lane represents the State responsibility section of a particular meaning, which clearly indicates that those activities are carried out by those objects.

Object flow: An object flow is a control flow that takes an object flow state as input or output. In an activity diagram, an object flow describes the relationship between an action state or an active state and an object, indicating how the action uses the object and how the action affects the object.

Activity diagram of UML9 map