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Information Systems Engineering

Information Systems Engineering. Class Diagram. diagrams UML. *Communication diagram(Collaboration diagram). Class Diagram. A Class diagram is used to display some of the classes and packages in your system

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Information Systems Engineering

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  1. Information Systems Engineering Class Diagram

  2. diagramsUML *Communication diagram(Collaboration diagram)

  3. 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

  4. Class Types: Class Utility • A class utilityis 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

  5. 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)

  6. 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

  7. 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

  8. 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 (#)

  9. Class Attributes Specifications cont. • Containment • By Value - the attribute is contained within the class • Reference - 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

  10. 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

  11. Relationships between classes Class A Superclass Class with parts name Class B Subclass Assembly Class Association (relationship) Inheritance (Generalization) (is-a, kind-of) Aggregation (Part-Of)

  12. Associations • A semantic relationship between two or more classes that specifies connections among their instances • Example: “An Employee works for a Company”

  13. Car Aggregation • A special form of association that models a whole-part relationship between an aggregate (the whole) and its parts. • Models a “is a part-part of” relationship. 4 Wheel wheels Whole Part

  14. Generalization • Indicates that objects of the specialized class (subclass) are substitutable for objects of the generalized class (super-class) • “is kind of” relationship An abstract class Shape Super Class Generalization relationship Sub Class Circle

  15. Generalization • A sub-class inherits from its super-class • Attributes • Operations • Relationships • A sub-class may • Add attributes and operations • Add relationships • Refine (override) inherited operations

  16. Head Arm Person Class Student Basic Class Diagram (Example) takes

  17. Practice • Draw the classes found in the ATM Withdraw Money use case • Classes • Attributes • Operations

  18. ATM Withdraw Money Class Diagram

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