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What is class diagram ? Draw class diagram for Library Management System.

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2016 - 2017 Assignment Question

Class diagram

In software engineering, a class diagram in the Unified Modeling Language (UML) is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the relationships among objects.

  • Classes

Classes represent an abstraction of entities with common characteristics. Associations represent the relationships between classes.

  • Active Classes

Active classes initiate and control the flow of activity, while passive classes store data and serve other classes. Illustrate active classes with a thicker border.

  • Visibility

Use visibility markers to signify who can access the information contained within a class. Private visibility, denoted with a - sign, hides information from anything outside the class partition. Public visibility, denoted with a + sign, allows all other classes to view the marked information. Protected visibility, denoted with a # sign, allows child classes to access information they inherited from a parent class.

  • Associations

Associations represent static relationships between classes. Place association names above, on, or below the association line. Use a filled arrow to indicate the direction of the relationship.

  • Multiplicity (Cardinality)

Place multiplicity notations near the ends of an association. 

  • Constraint

Place constraints inside curly braces {}.

  • Composition and Aggregation

Composition is a special type of aggregation that denotes a strong ownership between Class A, the whole, and Class B, its part. Illustrate composition with a filled diamond.

  • Generalization

Generalization is another name for inheritance or an "is a" relationship. 

Image source https://www.lucidchart.com/pages/class-diagram-for-library-management-system-UML


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