Appendix: Getting Started with UML

UML is made up of a number of different types of diagrams. Each gives the reader a slightly different perspective of the system's design. Some are high−level and intended to give you an understanding of the functionality in the system. Others are very detailed and include the specific classes and components that will be built to implement the system. Still others are midway between these two levels: They provide design details but from a higher−level perspective.

The set of diagrams gives you a complete picture of the system design. Different members of the team create different types of diagrams, and each is used by a different set of people. While building the system, the developers will refer to the diagrams to understand what classes and components need to be built. Later, when a team is maintaining the system, they can refer to the diagrams to understand the system structure, analyze the impact of a potential change, and document any design changes that were made.

UML is constantly being refined to incorporate new ideas and technologies. For example, it can now be used to model an XML DTD. As the object−oriented world changes, UML can change along with it. At the same time, though, it is a standard, and modifications to it are centrally managed. UML is controlled by the Object Management Group, which has members from large and small companies around the world.

Rational Software has developed a systems development lifecycle titled the Rational Unified Process (RUP). RUP complements UML by providing specific process steps, roles, responsibilities, guidelines, workflows, and templates that can be used to develop software. Although RUP complements UML, you may use UML without using RUP.

UML includes many different diagram types. Business Use Case diagrams are used to model the organization. Business workflow (activity) diagrams are used to show the processes within the organization. Use Case diagrams show the functionality to be provided by the system and the people and entities that interact with the system. Activity diagrams show the flow of logic through a use case. Sequence and Collaboration diagrams show the objects that are needed to implement the functionality of a use case, and include the messages between the objects. Statechart diagrams are used to model dynamic behavior, and are frequently used in real−time systems. Component diagrams show the components that will be created for the system and the relationships between them. Finally, Deployment diagrams are used to show the network structure and where the system will be deployed on the network.

Building a Business Use Case Diagram

A Business Use Case diagram is a mechanism for modeling the work done by the organization itself. The diagram contains business use cases, which are functions performed by the organization; business actors, which are entities outside the organization that interact with it; and business workers, which are roles within the organization.

The Business Use Case diagram gives someone an understanding of what the organization does and who interacts with it. It is supplemented by activity diagrams, which detail the workflows within the organization.

A business process team or a business analysis team typically creates the diagram. It is nontechnical, and can be used by any member of the organization to gain a better understanding of the organization.

To create a new Business Use Case diagram, follow these steps:

1.

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Right−click a package in the Use Case view.

2.

Select New → Use Case Diagram.

3.

Right−click the toolbar and select Customize.

4.

Add buttons for business actor, business use case, business worker, business entity, and organizational unit.

A Business Use Case diagram shows a subset of the business use cases, business workers, and business actors of the organization.

Follow these steps to add business actors to your diagram:

1.

Determine the business actors.

2.

Select the Business Actor toolbar button.

3.

Click in the Use Case diagram to add the actor.

4.

Name the actor.

A business actor is an individual, group, company, or other entity outside of the organization that directly interacts with the organization.

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Use these steps to add business workers to the diagram:

1.

Determine the business workers.

2.

Select the Business Worker toolbar button.

3.

Click in the Use Case diagram to add the worker.

4.

Name the worker.

A business worker is a role within the organization.

Follow these steps to add relationships between the business actors and business use cases:

1.

Select the Unidirectional Association toolbar button.

2.

Drag an arrow from the actor or business worker to the use case.

A communicates relationship between a business actor and a business use case shows how a business actor or business worker interacts with the organization.

Follow these steps to group the business actors, business workers, and business use cases into organization units.

1.

Select the Organization Unit toolbar button.

2.

Click inside a Business Use Case diagram to place the organization unit.

3.

In the browser, drag and drop business actors, business workers, business use cases, Business Use

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Case diagrams, and activity diagrams into the new organization unit.

An organization unit is used to group together business modeling elements such as business actors and business use cases. These units can help to organize the model and show how the company itself is organized.

Building a Workflow (Activity) Diagram

Activity diagrams are commonly used in two situations. In business modeling, they can be used to document the workflow of a process within the organization. In systems modeling, they can be used to document the flow of logic through a use case.

An activity diagram that focuses on workflow shows you the people or groups within the workflow, the steps in the process, decision points in the process, areas where steps in the process can occur in parallel, objects affected by the workflow, states of the objects, and transitions between steps in the process. UML contains notation for all of these items.

To create a new activity diagram:

1.

Right−click a use case or package in the Use Case view.

2.

Select New → Activity Diagram.

An activity diagram models a process in the organization. It can be used to analyze either existing or new processes. These types of diagrams are frequently used in business process re−engineering efforts or in any situation where the workflow is complex or undocumented.

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To partition your diagram into sections for each actor or worker's responsibilities, follow these steps:

1.

Determine the participants in the workflow.

2.

Select the Swimlane toolbar button.

3.

Click in the diagram to add the swimlane.

4.

Name the swimlane with the name of the role or group in the workflow.

A swimlane is a vertical section of the diagram that will contain all of the workflow steps that a particular person or group performs. You divide the diagram into many swimlanes, one for each person or group in the process.

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To add detailed steps to the diagram:

1.

Select the Activity toolbar button.

2.

Click in the diagram to add the activity.

3.

Name the activity.

An activity is a step in the workflow. It can contain actions, which are steps within the activity. The activity is placed in the swimlane of the individual or group that performs the activity.

Follow these steps to set the sequence of the activities:

1.

Select the Transition toolbar button.

2.

Drag an arrow from one activity to the next.

3.

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Right−click the transition arrow and select Open Specification.

4.

Optionally add an event and event arguments on the General tab.

5.

Optionally add a guard condition, action, send event, send event arguments, and send target on the Detail tab.

A transition shows how the process moves from one step (activity) to the next. An event triggers the movement from one activity to another. An event can have arguments. A guard condition controls when the transition can or cannot occur; the guard condition must be true for the transition to occur. An action occurs while the process is transitioning from one activity to another. It is typically a quick process that occurs as part of the transition itself. The send target suggests that, as part of the transition, a message is sent to some object. The send target is the object receiving the message. The send event is a message sent to another object. It may have arguments.

Follow these steps to add decision points to the logic:

1.

Select the Decision toolbar button.

2.

Click in the diagram to place the decision.

3.

Draw transitions from the decision to the activities that may occur after the decision.

4.

Place guard conditions on each transition arrow. The guard conditions will control which path is taken after the decision.

A decision point in the workflow indicates when the workflow can take two or more different paths. Transition arrows leading from the decision to activities show the different paths that the workflow can follow. Guard conditions on the transitions indicate under which conditions each path will be followed. Guard conditions must be mutually exclusive.

To add objects to the workflow:

1.

Select the Object toolbar button.

2.

Click inside the diagram to place the object.

3.

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