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Activity Diagrams

Activity diagrams

 Introduction

 Activities

 Nodes

• Action nodes

• Control nodes

• Object nodes

 Activity parameters

 Pins

Outline

Activity diagrams :

 A form of “object-oriented flowcharts”

 In UML 1 they were special cases of state machines; in

UML 2 they have new semantics, based on Petri Nets

 Greater flexibility to model different types of flow  Clearer distinction between activity diagrams and state machines

 Attached to modeling elements to describe behavior

 Typically attached to use cases, classes, components,

interfaces, and operations

 Can also be used to model business processes and

workflows

Introduction: What are activity diagrams?

Commonly used in:

 Analysis

• To model the flow of a use case
• To model the flow between use cases

 Design

• To model details of an operation
• To model details of an algorithm

 Business modeling

• To model a business process

 As always in modeling, it is important to keep them simple

and understandable by their intended audience

Introduction: Where are activity diagrams used?

 Activities and actions can have pre- and post-conditions

 Tokens (part of semantics but not shown graphically)

abstractly flow in the network and can represent:

• The flow of control
• An object
• Some data

 A token moves from a source node to a target node across

an edge depending on:

 Source node post-conditions

 Edge guard conditions

 Target node preconditions

Activities

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 Example of an activity (“send letter”), Fig. 14.2 [Arlow & Neustadt 2005] ** Activities

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 Activity diagrams have semantics based on Petri Nets  They model behavior using the token game  Tokens move through the network subject to conditions  Object nodes represent objects flowing around the system  Example of flow of control token, Fig. 14.5 [Arlow & Neustadt 2005]

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Activities

 Activity diagrams can be divided in partitions ( swimlanes ) using vertical, horizontal, or curved lines. Example, Fig. 14.6 [Arlow & Neustadt 2005]

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Activities

 After execution, the local postconditions are checked; if all are satisfied, the node simultaneously offers tokens to all its output edges (this is an implicit fork that may give rise to many flows)  Naming convention, Fig. 14.10 [Arlow & Neustadt 2005]

Action nodes

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 Types of action nodes , Table. 14.1 [Arlow & Neustadt 2005] ** Action nodes **

 An accept time event action node responds to time, Fig. 14.12 and Fig. 14.13 [Arlow & Neustadt 2005]

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Action nodes

 Control nodes manage the flow of control within an activity  Table 14.2 [Arlow & Neustadt 2005] shows the types of control nodes Control nodes **

 Examples of join and fork nodes, Fig. 14.17 [Arlow & Neustadt 2005] ** Control nodes

 Object nodes indicate that instances of a particular

classifier are available at a specific point in the activity

 They are labeled with the name of the classifier and

represent instances of that classifier or its subclasses

 The input and output edges are object flows

 Object flows are special types of flow that describe

movement of objects within the activity

 The objects are created and consumed by action nodes

 When an object node receives an object token on one of its

input edges, it offers this token to all its output edges, which

compete for the token.

Object nodes **