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UML Modeling
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The Unified Modeling Language (UML) is a standard modeling language for specifying, constructing, visualizing, and documenting   the artefacts of a software system.  The UML is appropriate for modeling systems ranging from enterprise information systems to distributed, embedded, and wed based applications.

UML fuses the concepts of Booch, OMT, and OOSE. The result  is a common, and widely usable modeling language. .

UML focuses on a standard modeling language, not a standard process.  Although UML must be applied in the context of a process, different organizations  and problem domains require different processes.  Therefore, the efforts focuses 1. on a common  meta model  and  2. a common notation which provides a human rendering. The UML authors promote a development process that is use-case driven, architecture centric, and iterative and incremental.

The UML specifies a modeling language that incorporates the object-oriented community's consensus on core modeling concepts. It allows deviations to be expressed in terms of its extension mechanisms.


What is UML


Most of us have heard the word UML tossed around so what exactly does this buzzword mean and why is it such a hot skill? 

UML stands for Unified Modeling Language. It is an object modeling technique that evolved as a result of the combined work of James Rumbaugh, Grady Booch and Ivar Jacobson, each of who had their own OO modeling notation a few years ago. The Object Management Group (OMG) adopted UML as a standard for software modeling in late 1997. UML is now the defacto standard for software modeling.

Why do we need a Modeling Language

There are two important reasons why we need a Modeling Language. First, the model provides a blueprint for developers so they know exactly what they need to build and for project managers so that they can precisely estimate the cost of a given project. Secondly and more importantly, UML is the bridge between technical developers and their non technical users; UML allows the developers to get a precise understanding of the exact requirements that the users have for the system being built. A UML model consists of a set of interrelated diagrams of the various parts of the system. 

Class Diagram

A class is a group of things with similar attributes and behavior. Take the example of a car. The name of the class is "car" followed by the attributes (manufacturer, model, year, license plate number) of the class and the actions that are performed by objects of the class (start car (), stop car (), drive car (), reverse car (), brake car ()).

license plate number
start car ()
stop car ()
drive car ()
reverse car ()
brake car ()

Object Diagram

An object is a particular instance of a class. In UML, the object diagram specifies the class name on the right of the colon and the object name on the left of the colon and both are underlined.

my car : car


State Diagram

At a specific point in time an object is usually in one of many states. The state diagram shows the transitions from one state to the next. A dot represents the start state and a circle with a dot in the middle represents the end state. In our example,

. -> start -> reverse -> drive -> brake ->stop -> 0

Use Case Diagram

A use case is a description of a scenario by the user. Use case statements and diagrams are used by the users to clearly communicate their requirements to the development team.

Sequence Diagram

The sequence diagram provides a dynamic view of the system behavior. For instance in our example, the sequence diagram would show the interactions between the various mechanisms within the car for each action such as starting a car, stopping a car and so on.

Deployment Diagram

The UML deployment diagram shows the actual hardware required to implement a system.

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