01-03-2013, 11:32 AM
Introduction to UML and Rational Rose
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INTRODUCTION
The UML is a language for specifying, constructing, visualizing, and documenting the software system and its components. The UML is a graphical language with sets of rules and semantics. The rules and semantics of a model are expressed in English in a form known as OCL (Object Constraint Language). OCL uses simple logic for specifying the properties of a system. The UML is not intended to be a visual programming language. However it has a much closer mapping to object-oriented programming languages, so that the best of both can be obtained. The UML is much simpler than other methods preceding it. UML is appropriate for modeling systems, ranging from enterprise information system to distributed web based application and even to real time embedded system. It is a very expensive language addressing all views needed to develop and then to display system even though understand to use. Learning to apply UML effectively starts forming a conceptual mode of languages which requires learning.
Use Case Diagram
The behavior of the system under development (i.e. what functionality must be provided by the system) is documented in a use case model that illustrates the system's intended functions (use cases), its surroundings (actors), and relationships between the use cases and actors (use case diagrams).
Actors
• Are NOT part of the system – they represent anyone or anything that must interact with the system.
• Only input information to the system.
• Only receive information from the system.
• Both input to and receive information from the system.
• Represented in UML as a stickman.
Use Case
• A sequence of transactions performed by a system that yields a
measurable result of values for a particular actor
• A use case typically represents a major piece of functionality
that is complete from beginning to end. A use case must
deliver something of value to an actor.
Documenting Flow of events
Background
Each use case is documented with a flow of events. The flow of events for a use case is a description of the events needed to accomplish the required behavior of the use case. Activity diagrams may also be created at this stage in the life cycle. These diagrams represent the dynamics of the system. They are flow charts that are used to show the workflow of a system; that is, they show the flow of control from one activity to another in the system,
Flow of Events
A description of events required to accomplish the behavior of the use case, that:
• Show WHAT the system should do, not HOW the system does it.
• Written in the language of the domain, not in terms of implementation.
• Written from an actor point of view.
Activity Diagram
Activity diagrams are flow charts that are used to show the workflow of a system. They also:
• Represent the dynamics of the system.
• Show the flow of control from activity to activity in the system.
• Show what activities can be done in parallel, and any alternate paths through the flow.
Activity diagrams may be created to represent the flow across use cases or they may be created to represent the flow within a particular use case. Later in the life cycle, activity diagrams may be created to show the workflow for an operation.
State Transition Details
• A state transition may have an action and/or guard condition associated with it and it may also trigger an event.
• An action is the behavior that occurs when the state transition occurs.
• An event is a message that is sent to another object in the system.
• A guard condition is a Boolean expression of attribute values that allows a state transition only if the condition is true.
• Both actions and guards are behaviors of the object and typically become operations. Also they are usually private operations (used by the object itself)
• Actions that accompany all state transitions into a state may be placed as an entry action within the state.
• Actions that accompany all state transitions out of a state may be placed as exit actions within the state
• A behavior that occurs within the state is called an activity.
• An activity starts when the state is entered and either completes or is interrupted by an outgoing state transition.