CS 501: Software Engineering Fall 2000 Lecture 11 Object-Oriented Design I

2 Administration Preparation for presentation -- Recitation Section, Monday October 2 -- Not all members of team need be present Fall Programming Contest for this year will be on October 14th, organized by the ACSU and David Kempe.

3 What is in a Requirements Document? Example (Web Butler and Web Site Profiler) Run web data collection in real time or batch mode How are jobs started? Job parameters How are the parameters set up (interactive, edit file,...)? What are the parameters (specify)? Can job parameters be stored and used again? If so, how? Job monitoring What feedback is given while job is running? Can the user pause or break a job? If so, are the results retained?

4 What is in a Requirements Document? Remember The requirements document specifies the functionality that you plan to deliver to the client It must be comprehensive and detailed. Everything must be written out -- no hand waving! The requirements document is likely to be several times as long as Assignment 1.

5 Assignment 2 -- Individual Parts One approach: With your document, include a list of who contributed what part to the Requirements study, e.g., Person A Requirements analysis for database design (member of team of 3), wrote Section 3.1 of document, worked with client to identify software needs. Person B Prepared visual aids for presentation, edited entire document, specified the security needs and wrote Section 4.2.

6 The Waterfall Model Requirements Definition Implementation and Unit Testing Integration and System Testing Operation and Maintenance System and Software design

7 Useful Texts Grady Booch, James Rumbaugh, Ivar Jacobson, The Unified Modeling Language. Addison-Wesley Grady Booch, Object-Oriented Analysis and Design with Applications, second edition. Benjamin/Cummings Rob Pooley, Perdita Stevens, Using UML Software Engineering with Objects and Components. Addison-Wesley 1999.

8 The Importance of Modeling A model is a simplification of reality. We build models so that we can better understand the system we are developing. We build models of complex system because we cannot comprehend such a system in its entirety. Models can be informal or formal. The more complex the project the more valuable a formal model becomes. BRJ

9 Principles of Modeling The choice of what models to create has a profound influence on how a problem is attacked and how a solution is shaped. Every model can be expressed at different levels of precision. The best models are connected to reality. No single model is sufficient. Every nontrivial system is best approached through a small set of nearly independent models. BRJ

10 The Unified Modeling Language UML is a standard language for modeling software systems. Serves as a bridge between the requirements specification and the implementation. Provides a means to specify and document the design of a software system. Is process and programming language independent. Is particularly suited to object-oriented program development.

11 Notation: Classes Window origin size open() close() move() display() name attributes operations A class is a description of a set of objects that share the same attributes, operations, relationships and semantics.

12 Notation: Interface An interface is a collection of operations that specify a service of a class or component, i.e., the externally visible behavior of that element. ISpelling

13 Notation: Collaboration & Use Case Place order A use case is a description of a set of sequence of actions that a system performs that yields an observable result. Chain of responsibility A collaboration defines an interaction, i.e., a society of roles and other elements that work together to provide some cooperative behavior.

14 Notation: Active Class EventManager eventlist suspend() flush() An active class is a class whose objects own one or more processes or threads and therefore can initiate control activity.

15 Notation: Component & Node orderform.java A component is a physical and replaceable part of a system that conforms to and provides the realization of a set of interfaces. Server A node is a physical element that exists at run time and represents a computational resource.

16 Notation: Behavioral Things: Messages & States display An interaction is a behavior that comprises a set of messages exchanged among a set of objects within a particular context to accomplish a specific purpose. Waiting A state machine is a behavior that specifies the sequence of states an object or an interaction goes through during its lifetime in response to events.

17 Notation: Grouping and Annotation A package is a general-purpose mechanism for organizing elements into groups. Business rules return copy of self A note is a symbol for rendering constraints and comments attached to an element or a collection of elements.

18 Notation: Relationships A dependency is a semantic relationship between two things in which a change to one may effect the semantics of the other * employer employee An association is a structural relationship that describes a set of links, a link being a connection among objects.

19 Notation: Relationships (continued) A generalization is a specialization/generalization relationship is which objects of the specialized element (child) are substitutable for objects of the generalized element (parent). childparent A realization is a semantic relationship between classifiers, wherein one classifier specifies a contract that another classifier guarantees to carry out.

20 Diagrams in UML A diagram is the graphical representation of a set of elements, usually rendered as a connected graph of vertices (things) and arcs (relationships). Class diagram shows a set of classes, interfaces, and collaborations with their relationships. Object diagram shows a set of objects and their relationships. Use case diagram shows a set of use cases and actors (a special kind of class) and their relationships.

21 Diagrams in UML (continued) Interaction diagram shows an interaction, consisting of a set of objects and the relationships, including the messages that may be dispatched among them. => A sequence diagram emphasizes the time ordering. => A collaboration diagram emphasizes the structural organization of the objects that send and receive messages.

22 Diagrams in UML (continued) Statechart diagram shows a state machine consisting of states, transitions, events, and activities. Activity diagram is a statechart diagram that shows the flow from activity to activity within a system. Component diagram shows the organization and dependencies among a set of components. Deployment diagram shows the configuration of processing nodes and the components that live on them.

23 The HelloWorld Example HelloWorld paint() class name operations

24 Abstraction for HelloWorld HelloWorld paint() g.drawString ("HelloWorld", 0, 10)" class name operations annotation

25 The "Hello, World" Example import java.awt.Graphics; class HelloWorld extends java.applet.Applet { public void paint (Graphics g) { g.drawString ("Hello, World!", 10, 10); } Example from: BJR

26 Class Diagram Applet HelloWorld paint() Graphics generalization dependency Note that the Applet and Graphics classes are shown elided.

27 Class Inheritance Diagram Object Component Container Panel Applet HelloWorld ImageObserver interface

28 Packaging Classes applet awt lang HelloWorld java Graphics package

29 Notation for Classes and Objects Classes Objects AnyClass attribute1 attribute2 operation1() operation2() AnyClass or anObject:AnyClass :AnyClass anObject The names of objects are underlined. or