Unified Modeling Language- (UML)

Brief Background

UML is a language for specifying,visualizing ,documenting and constructing the artifacts of software systems,as well as for business modeling and other non-software systems.

UML has been developed by Grady  Booch, James Rumbaugh and Ivar Jacobson.

Goals of UML are :

1. To model systems using Object oriented concepts.
2. To establish an explicit coupling to conceptual as well as executable artifacts
3. To address the issues of scale inherent in complex , mission critical systems.
4. To create a modeling language that can be used by humans as well as machines. 

Understanding the thirteen diagrams of UML 2.x is an important part of understanding OO development. Although there is far more to modeling than just the UML the reality is the UML defines the standard modeling artifacts when it comes to object technology.

There are three classifications of UML diagrams:

• Behavior diagrams. A type of diagram that depicts behavioral features of a system or business process. This includes activity, state machine, and use case diagrams as well as the four interaction diagrams.
• Interaction diagrams. A subset of behavior diagrams which emphasize object interactions. This includes communication, interaction overview, sequence, and timing diagrams.
• Structure diagrams. A type of diagram that depicts the elements of a specification that are irrespective of time. This includes class, composite structure, component, deployment, object, and package diagrams.

The Diagrams of UML 2.

Activity Diagram

Depicts high-level business processes, including data flow, or to model the logic of complex logic within a system. 

Class Diagram

Shows a collection of static model elements such as classes and types, their contents, and their relationships.

Communication Diagram

Shows instances of classes, their interrelationships, and the message flow between them. Communication diagrams typically focus on the structural organization of objects that send and receive messages. Formerly called a Collaboration Diagram.

Component Diagram

Depicts the components that compose an application, system, or enterprise. The components, their interrelationships, interactions, and their public interfaces are depicted.

Composite Structure Diagram

Depicts the internal structure of a classifier (such as a class, component, or use case), including the interaction points of the classifier to other parts of the system.

Deployment Diagram

Shows the execution architecture of systems. This includes nodes, either hardware or software execution environments, as well as the middleware connecting them.

Interaction Overview Diagram

A variant of an activity diagram which overviews the control flow within a system or business process. Each node/activity within the diagram can represent another interaction diagram.

Object Diagram

Depicts objects and their relationships at a point in time, typically a special case of either a class diagram or a communication diagram.

Package Diagram

Shows how model elements are organized into packages as well as the dependencies between packages.

Sequence Diagram

Models the sequential logic, in effect the time ordering of messages between classifiers.

State Machine Diagram

Describes the states an object or interaction may be in, as well as the transitions between states. Formerly referred to as a state diagram, state chart diagram, or a state-transition diagram.

 Timing Diagram

Depicts the change in state or condition of a classifier instance or role over time. Typically used to show the change in state of an object over time in response to external events.

Use Case Diagram

Shows use cases, actors, and their interrelationships.