1 SWE Introduction to Software Engineering Lecture 15 – System Modeling Using UML

2 Lecture Objectives Describe the basic UML notation associated with analysis; and Introduce new types of analysis objects. Discuss inputs for Design Model.

3 Aims of Analysis Model To provide a ‘logical model’ of the system, in terms of: Classes Relationships ‘How to get the thing right, now and in the future’?

4 Producing an Analysis Model Draft initial class diagram Re-examine behavior in use cases and objects Refine class diagram Execute check Revise class diagram Group classes into packages

5 Analysis Model Inputs & Outputs Inputs Use cases and use case models Outputs Class roles and responsibilities [text] Use case description in terms of classes and operations [text + use case] Completed analysis model [class and package diagram]

6 Classes in UML Class Name Attribute name : Type Operation name (parameter type) : result type Class Name

7 Objects in UML objectName: className Attribute name : type = value (same operations for all instances of a class) objectName: className Display (on: Surface) Rotate (angle: integer)

8 UML Generalization

9 Associations in UML

10 Class Diagram in UML Class diagrams Show logical, static structure of system Provide core of ‘unified model’ Generation of initial class diagram from problem domain object list Classes of objects Associations / attributes Inheritance relationships

11 Initial Class Diagram - Example

12 Exploiting Use Cases Employ classes and use cases, one by one To describe roles and responsibilities of each class To distribute behavior specified in use cases To ensure that there is a class for every behavior

13 Roles of Classes Interface classes For everything concerned with system interfaces Entity classes For persistent information and behavior coupled to it. Control classes For functionality not normally tied to other classes

14 Roles of Classes Integrated into UML as stereotypes

15 Interface Classes Contains functionality directly dependent on system environment Definition focuses on interaction between actor and use cases

16 Interface Classes

17 Entity Classes and their Attributes Purposes of entity classes: To store information persisting after completion of a use cases To define behavior for manipulating this information.

18 Entity Classes and their Attributes

19 Packages Packages are necessary Because of large numbers of classes To provide optional functionality To minimize effect of change Packages should have a Tight functional coupling Packages my contain nested packages

20 Example – Recycling Packages

21 Key points Analysis Model Outputs Class roles Use case description in terms of classes Completed analysis model Sub-system diagrams