Using Diagrams to Represent Program Structure OMT and UML Some pictures and material are from “Design Patterns” by Gamma et al

Outline l why diagrams l diagram types l class diagram elements n class n aggregation n inheritance n instantiation l class diagram examples l object diagram l use case diagram l interaction diagram 2

Why Diagrams l diagrams is a way to capture the essential aspects of the program n have an overview of the whole program n see the important relationships between elements of program n get the picture of the program before it is coded l standardized as part of n object modeling technique (OMT) – Rumbaugh, Blaha, et al 1991 n universal modeling language (UML) – Rational Rose Inc. and other companies l used in program planning, development and documentation l language independent (not necessarily C++) 3

Diagram Types l structure diagram – emphasizes what constructs must be present in the modeled system n class diagram – the system classes, attributes, their relationships n object diagram – a view of the modeled system at a specific execution instance l behavior diagram – emphasizes what actions must happen in the system n use-case diagram – system functionality in terms of interaction with outside actors n interaction diagram – flow of control and data among constructs 4

Classes l operations – member functions/methods l instance variables – member variables/attributes class Example{ public: void showchar(); string getstring(); private: char c; string str; }; class BankAccount{ public: void deposit(dollars amount); void withdrawal(dollars amount); private: string owner; dollars balance; }; Example showchar(): void getstring(): string c: char str: string ClassName oper2(): returnType oper1(parName: parType): rType instVar1: Type instVar2: Type 5

Aggregation l if class contains instances (objects) of other classes the class aggregates them l if class aggregates more than one instance of the same class it is shown diagramatically l multiplicity - shows how many instances of objects on each side 6

Inheritance, Reference and Instantiation Class inheritance l class contains a reference to another l object creation (class instantiation) is done by a method of another class Additional comments 7

Visibility - private member + public member 8

Example Class Diagram 1 9

Example Class Diagram 2 10

Example Class Diagram 3 l blah 11

Object Diagram l shows objects and references as the program is executed l what would be a class and an object diagram for an object with dynamically allocated members? 12

Use Case Diagrams l written description of the system’s behavior regarding tasks or requirements l captures interactions between actors (outside entities) and the system through use cases use case actor 13

Interaction (Sequence) Diagram l shows order in which requests (methods) between objects are executed - scenario, typically within a single use case n boxes – processes (function invocation) in each object n lines – messages (interaction) between objects n lifeline – vertical dashed line represents objects’ existence 14

Interaction Diagram Examples 15

Interaction Diagram Examples 2 16

Questions on Diagrams l What is the purpose for the use of diagrams l What is the difference between structure and behavior diagrams? l What types of structure diagrams we have studied? Behavior diagrams? l How is class denoted on a structure diagram? l What is aggregator/agregatee? How is their relationship denoted? l What is multiplicity and how is it denoted? l What is visibility and hwo is it denoted? l How are objects denoted on an a structure diagram? l What diagram uses use cases, actors? What is system boundary? l What do boxes and lines and crosses represent in a flow diagram? 17

Battleship Class and Object Diagrams 18

Battleship Use Case and Interaction Diagrams 19