Nov 06

UML

UML is a standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems.

UML was created by Object Management Group (OMG) and UML 1.0 specification draft was proposed to the OMG in January 1997.

OMG is continuously putting effort to make a truly industry standard.

  • UML stands for Unified Modeling Language.
  • UML is different from the other common programming languages like C++, Java, COBOL etc.
  • UML is a pictorial language used to make software blue prints.

So UML can be described as a general purpose visual modeling language to visualize, specify, construct and document software system. Although UML is generally used to model software systems but it is not limited within this boundary. It is also used to model non software systems as well like process flow in a manufacturing unit etc.

UML is not a programming language but tools can be used to generate code in various languages using UML diagrams. UML has a direct relation with object oriented analysis and design. After some standardization UML is become an OMG (Object Management Group) standard.

Goals of UML:

A picture is worth a thousand words, this absolutely fits while discussing about UML. Object oriented concepts were introduced much earlier than UML. So at that time there were no standard methodologies to organize and consolidate the object oriented development. At that point of time UML came into picture.

There are a number of goals for developing UML but the most important is to define some general purpose modeling language which all modelers can use and also it needs to be made simple to understand and use.

UML diagrams are not only made for developers but also for business users, common people and anybody interested to understand the system. The system can be a software or non software. So it must be clear that UML is not a development method rather it accompanies with processes to make a successful system.

At the conclusion the goal of UML can be defined as a simple modeling mechanism to model all possible practical systems in today.s complex environment.

A conceptual model of UML:

To understand conceptual model of UML first we need to clarify What is a conceptual model? andWhy a conceptual model is at all required?

  • A conceptual model can be defined as a model which is made of concepts and their relationships.
  • A conceptual model is the first step before drawing a UML diagram. It helps to understand the entities in the real world and how they interact with each other.

As UML describes the real time systems it is very important to make a conceptual model and then proceed gradually. Conceptual model of UML can be mastered by learning the following three major elements:

  • UML building blocks
  • Rules to connect the building blocks
  • Common mechanisms of UML

Object oriented concepts:

UML can be described as the successor of object oriented analysis and design.

An object contains both data and methods that control the data. The data represents the state of the object. A class describes an object and they also form hierarchy to model real world system. The hierarchy is represented as inheritance and the classes can also be associated in different manners as per the requirement.

The objects are the real world entities that exist around us and the basic concepts like abstraction, encapsulation, inheritance, polymorphism all can be represented using UML.

So UML is powerful enough to represent all the concepts exists in object oriented analysis and design. UML diagrams are representation of object oriented concepts only. So before learning UML, it becomes important to understand OO concepts in details.

Following are some fundamental concepts of object oriented world:

  • Objects: Objects represent an entity and the basic building block.
  • Class: Class is the blue print of an object.
  • Abstraction: Abstraction represents the behavior of an real world entity.
  • Encapsulation: Encapsulation is the mechanism of binding the data together and hiding them from outside world.
  • Inheritance: Inheritance is the mechanism of making new classes from existing one.
  • Polymorphism: It defines the mechanism to exists in different forms.

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