Common Mechanisms of UML

BASIC STRUCTURAL MODELING-I
Classes 

• In object-oriented programming, programs are organized as cooperative collections of objects 
• All objects are instances of a class 
• A class is a description of a set of objects that share the same attributes, behaviors, relationships and semantics 
• Hence, class becomes the important building block of any object-oriented system 
• A class provides a blueprint for creating objects 
• It can represent a software, a hardware or even a conceptual thing 
• A class usually collaborates with other classes 
• It is shown as a rectangle with three compartments that includes its name, attributes and operations 

A Class typically has:

-Names -Attributes -Operations -Responsibilities

Names:

• Extracted from the problem domain (statement) 
• Nouns or noun phrases 
• Concise and descriptive 

• Path name is a class name prefixed by the name of the package in which that class lives 

Attributes: 

• Describe common characteristics of the objects in the class 
• The values of attributes determine the state of an object 
• For example, the value of the year attribute of a student indicates which year the student is studying
• They are usually nouns extracted from the problem statement 

Operations:

• Operations indicate the services provided by the objects of the class
• They are usually verbs or verb phrases from the problem statement

Responsibilities:

• A Contract or obligations of a class to the users of the class means that an object of the class has to fulfill these responsibilities when requested by other objects