Class diagram is a static representation used in the programming field to describe the structure of a system, presenting its classes, attributes, operations and the relationships between objects.
This type of representation is very useful in the development of computing systems and software , as it defines all the classes that the system needs to have and serves as a basis for the construction of other diagrams that define the type of communication, sequence and states of the systems.
The class diagram is the central part of the Unified Modeling Language (UML ) . It represents the main purposes of UML, having the function of separating the design elements from the coding of the system.
This language helps model various subsets of diagrams, including behavior, interaction, and structure diagrams. It is typically used by engineers to document software architecture .
Class Diagram Components
The diagram items that make up a class diagram can represent the classes that will actually be programmed, as well as the main objects or the interaction between classes and objects in the system. These items are:
Class
Abstract element that represents a set of objects. It contains the specification of the object, its characteristics, attributes and methods.
Attribute
It defines the characteristics of the class such as visibility, name, data type, multiplicity, initial value and property.
Visibility can be public (represented by the + symbol) or private (represented by the – symbol). When it is public, other classes can have access to the attribute and when it is private, only the class itself has access .
It can also be protected (represented by the # symbol) or it can be package-attributed (represented by the ~ symbol), where the attribute is accessed by the class’s relationship with the external class.
The name is the identification of the attribute and the data type indicates the specification of the attribute data, as well as its initial value and its properties , which depend on the language used in the programming. Multiplicity indicates the possibility of the attribute to make relations with other classes.
Operation
It deals with the function required of an abstract object. This component also contains characteristics such as name, visibility and parameters.
Association
This component deals with the ability of classes to relate to each other. It can also contain the name, multiplicity, and navigation type, which indicates where the class’s information comes from and where it will go.
In terms of structure, the class diagram is presented in such a way that the shape of the class itself consists of a rectangle with three lines.
The top line contains the class name, the middle line contains the class attributes, and the bottom line expresses the methods or operations that the class can use. In a diagram, classes and subclasses are grouped together to show the static relationship between each object.
