Information Systems Engineering Class Diagram 1. diagrams UML 2 *Communication diagram(Collaboration diagram)

Information Systems Engineering

Class Diagram

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diagrams UML

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*Communication diagram(Collaboration diagram)

Class Diagram

• A Class diagram is used to display some of the classes and packages in your system

• It gives you a static picture of the pieces in the system and of the relationships between them

• They help the developers see and plan the structure of the system before the code is written, helping to ensure that the system is well designed from the beginning

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Class Types: Class Utility

• A class utility is a collection of operations

• Ex: you may have some mathematical functions—squareroot(), cuberoot(), and so on—that are used throughout your system but don't fit well into any particular class

• These functions can be gathered together and encapsulated into a class utility for use by the other classes in the system

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Class Types: Abstract Class

• Abstract Class - is a class that will not be instantiated. In other words, if Class A is abstract, there will never be any objects of Type A in memory.

•it exists extensively for inheritance and it must be inherited. There are scenarios in which it is useful to define classes that is not intended to instantiate; because such classes normally are used as base-classes in inheritance hierarchies.(Animal class Example)

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Class Specifications

• Class Name - Unique Name, No spaces, Short, Starting with an upper-case letter

• Class Visibility • Public - the class can be seen by all of the other classes in the system• Protected or private - the class can be seen in nested classes

• Class Multiplicity - The number of instances that you expect to have of a class

• Storage Requirements for a Class - The amount of memory you expect each object of the class to require

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Class Specifications cont.

• Class Persistence • Persistent – the information in objects of the class will be saved to a database or some other form of persistent storage• Transient – the information in objects of the class will not be saved to persistent storage

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Class Attributes Specifications

• Data Type (e.g. string, double, int, etc..)

• Initial Value – Not required

• Visibility• Public - the attribute is visible to all other classes ( + )• Private - the attribute is not visible to any other class ( - )• Protected - the class and any of its descendants have access

to the attribute (#)

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Class Attributes Specifications cont.

• Containment By Value - the attribute is contained within the classReference - the attribute is located outside the class, but

the class has a pointer to it

• Static Attribute - Shared by all instances of the class

• Derived Attribute - Created from other attributes , Ex. Area is created from the height and width

attributes

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Class Operations

• An operation is a behavior associated with a class

• An operation has three parts: • The Operation Name• The Operation Parameters • The Operation Return Type

• The parameters are arguments the operation receives as input. The return type is the output of the operation

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Practice

• Draw the classes found in the ATM Withdraw Money use case

•Classes•Attributes•Operations

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ATM Withdraw Money Class Diagram

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