CS 501: Software EngineeringAdministrationThe Waterfall ModelProgram DesignThe Unified Modeling LanguageUML ModelsDiagrams in UMLDiagrams in UML (continued)Slide 9AnnotationClass DiagramsNotation: GroupingPackaging ClassesThe "Hello, World!" ExampleThe HelloWorld ExampleAbstraction for HelloWorldNotation: RelationshipsRelationshipsNotation: Relationships (continued)GeneralizationNotation: InterfaceClass Inheritance DiagramModeling ClassesNoun Identification: A Library ExampleSlide 25Candidate ClassesRelations between ClassesOperationsClass DiagramRough Sketch: Wholesale SystemSlide 31Slide 32Expanding a Class: Modeling Financial InformationModeling InvoiceLessons LearnedLevels of Abstraction1CS 501 Spring 2005CS 501: Software EngineeringLecture 15Object Oriented Design 12CS 501 Spring 2005AdministrationProjectsNow is the time to press ahead with final design and implementation.Allow plenty of time for testing, for making small changes, and for documentation and packaging.3CS 501 Spring 2005The Waterfall ModelRequirements analysisSystem designTestingOperation & maintenanceProgram designCodingAcceptanceRequirementsDesignImplementationFeasibility study4CS 501 Spring 2005Program DesignThe task of program design is to represent the software system functions in a form that can be transformed into one or more executable programs.Given a system architecture, the program design specifies:•programs, components, packages, classes and class hierarchies•interfaces, protocols•security mechanisms, operational procedures5CS 501 Spring 2005The Unified Modeling LanguageUML 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.6CS 501 Spring 2005UML ModelsA UML model consists of:(a) A diagram. This gives a general overview of the model, showing the principal elements and how they relate to each other.(b) A specification. This provides details about each element of the model. Specification for models used in program design should have sufficient detail that they can be used to write code from.A diagram without a specification is not a complete model, but may be very useful as a design tool.7CS 501 Spring 2005Diagrams in UMLA 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.8CS 501 Spring 2005Diagrams in UML (continued)An 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.9CS 501 Spring 2005Diagrams 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.10CS 501 Spring 2005Annotationsome text noteA note is a symbol for rendering constraints and comments attached to an element or a collection of elements.11CS 501 Spring 2005Class Diagrams Windoworiginsizeopen()close()move()display()nameattributesoperationsresponsibilities (optional text)A class is a description of a set of objects that share the same attributes, operations, relationships and semantics.12CS 501 Spring 2005Notation: GroupingA package is a general-purpose mechanism for organizing elements into groups.Business rules13CS 501 Spring 2005Packaging ClassesappletawtlangHelloWorldjavaGraphicspackage14CS 501 Spring 2005The "Hello, World!" Exampleimport java.awt.Graphics;class HelloWorld extends java.applet.Applet { public void paint (Graphics g) { g.drawString ("Hello, World!", 10, 10); }}Example from: BJR15CS 501 Spring 2005The HelloWorld ExampleHelloWorldpaint()classnameoperations16CS 501 Spring 2005Abstraction for HelloWorldHelloWorldpaint()g.drawString ("HelloWorld", 0, 10)"classnameoperationsannotation17CS 501 Spring 2005Notation: RelationshipsA dependency is a semantic relationship between two things in which a change to one may effect the semantics of the other.0..1 *employer employeeAn association is a structural relationship that describes a set of links, a link being a connection among objects.18CS 501 Spring 2005RelationshipsParkingGarageParkingSpacelocationis_available()11 ... *19CS 501 Spring 2005Notation: 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).child parentA realization is a semantic relationship between classifiers, wherein one classifier specifies a contract that another classifier guarantees to carry out.20CS 501 Spring 2005GeneralizationAppletHelloWorld paint()GraphicsgeneralizationdependencyNote that the Applet and Graphics classes are shown elided, i.e., just the name is shown, not the attributes or operations.21CS 501 Spring 2005Notation: InterfaceAn interface is a collection of operations that specify a service of a class or component, i.e., the externally visible behavior of that element.ISpelling22CS 501 Spring 2005Class Inheritance DiagramObjectComponentContainerPanelAppletHelloWorldImageObserverinterface23CS 501 Spring 2005Modeling ClassesGiven a real-life system, how do you decide what classes to use?• What terms do the users and implementers use to describe the system? They are candidates for classes.• Is each candidate class crisply defined? • For each class, what is its set of responsibilities? Are the responsibilities evenly balanced among the classes?•
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