Sequence Diagrams and Collaboration DiagramsIntroduction/AgendaObject Oriented DesignSequence DiagramSequence Diagram - ObjectsSequence Diagram – Time & MessagesTypes of MessagesSequence Diagram – CompilationBranching Flow: flow goes to different objects [if condition is met]Alternative Flow: flow changes to alternative lifeline branch of the same objectSequence diagram -exampleSystem Design PrinciplesReading from a command file - exampleSequence Diagram – URS Add Subject ScenarioCreating and Deleting objectsCollaboration DiagramsCollaboration DiagramsCollaboration Diagram – URS Add Subject ScenarioSlide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25URS -High Level Class DiagramSlide 27Use Case Vs ScenariosSequence Diagram – Enroll Student for subject successfullyCollaboration Diagram – Enroll Student in Subject ScenarioCollaboration Diagram – Enroll Student in Subject subject - implementationSequence Diagram – Enroll Student for subject - Failure1Sequence Diagramsand Collaboration Diagrams Rajkumar BuyyaGrid Computing and Distributed Systems (GRIDS) LaboratoryDept. of Computer Science and Software EngineeringUniversity of Melbourne, Australiahttp://www.cs.mu.oz.au/~raj or http://www.buyya.com2Introduction/AgendaPieces of UML:Structural DiagramsClass and object diagramComponent and Deployment DiagramBehavioural Diagrams Use Case DiagramActivity DiagramSequence DiagramCollaboration DiagramState Chart DiagramLearned so far: Use case diagram, class and object diagram, class relationshipsToday we will focus on:Sequence DiagramCollaboration Diagram3Object Oriented DesignDesign consists of the following steps :Refine the class diagram.Draw the interaction diagrams for the system.Sequence DiagramCollaboration DiagramIf objects go through complex state transitions – statechart diagramsDo the above steps iteratively as needed.4Sequence DiagramShows how objects communicate with each other over time.That is, sequence diagrams are used to model object interactions arranged in time sequence and to distribute use case behavior to classes.They can also be used to illustrate all the paths a particular use case can ultimately produce.The sequence diagram consists of Active Objects, Messages represented as solid-line arrows, and Time represented as a vertical progression.5Sequence Diagram - ObjectsA life line illustrates what is happening to an object in a chronological fashion.:NameLife lineActivationObject6Sequence Diagram – Time & MessagesMessages are used to illustrate communication between different active objects of a sequence diagram.:Name1 :Name2Message TwoActorMessage One7Types of MessagesSynchronous (flow interrupt until the message has completed.Asynchronous (don’t wait for response)Flat – no distinction between sysn/asyncReturn – control flow has returned to the caller.8Sequence Diagram – Compilation:Compiler LinkerActorCompileFileSystemLoad FilesSave OBJ FilesCompile filesLinkLoad OBJ filesLink OBJ filesWrite EXE file9Branching Flow: flow goes to different objects [if condition is met]:Editor FileSystemLoad File:BinaryViewer :TextViewer[text file][binary file]10Alternative Flow: flow changes to alternative lifeline branch of the same objectEditorActorExit AppFileSystem[delete file][save file]11Sequence diagram -exampleUse case Add Subject Use Case to URS (University Record System):ScenarioScenario 1 : Subject gets added successfully.Scenario 2 : Adding the subject fails because the subject is already in the database.12System Design PrinciplesSystem input can take different forms. E.g.From a graphical user interfaceFrom a command fileURS system should be designed such that the functionality can be re-used.Command reading and functionality implementation have to be separated.13Reading from a command file - exampleclass URS{ public static void main(String[] args){ URSDatabase u = new URSDatabase(); //Read command from file; while ( not end of file) {u.procCommand(cmd);//Read next commad;}//Close file}}14execute()Sequence Diagram – URS Add Subject Scenariou:URSDatabaseprocCmd(cmd)sub1:SubjectSubject(id,name)<< create >>parseCommand(cmd)addSubject(sub1){transient}a:AddSubCmd << create >>[if cmdN = ADDSUB]AddSubCmd(u,cmdA)15Creating and Deleting objectsc:Client:Transactionp: ODBProxysetVales(a,d,3,4)<<destroy>><<create>>committedsetAction(a, d, 0){transient}16Collaboration Diagrams17Collaboration DiagramsClass diagrams indicates what classes are part of our system, what they offer, how they relate, but they don’t tell us how they communicate.Collaboration diagrams show (used to model) how objects interact and their roles.They are very similar to sequence diagrams. Actually they are considered as a cross between class and sequence diagram.Sequence Diagrams are arranged according to Time.Collaboration Diagrams represent the structural organization of object.[Both sequence and collaboration diagrams are called interaction diagrams]18Collaboration Diagram – URS Add Subject Scenariou:URSDatabase<<self>>a:AddSubCmd 2:[if cmdN = ADDSUB]AddSubCmd(u,cmdA) <<local>>{new}{transient}3: execute()3.2: addSubject(sub1)1:parseCommand(cmd)procCmd(cmd)sub1:Subject 3.1: Subject(id,name){new}19Collaboration Diagram – URS Add Subject Scenariou:URSDatabase<<self>>1:parseCommand(cmd)procCommand(cmd)class URSDatabase{ private String cmdN; private String cmdA; private parseCommand(String cmd){ cmdN = …. cmdA = …. } public procCommand(String cmd){ parseCommand(cmd); }}20Collaboration Diagram – URS Add Subject Scenariou:URSDatabasea:AddSubCmd 2: AddSubCmd(u,cmdA){new}{transient}class URSDatabase{ private String cmdN; private String cmdA; public procCommand(String cmd){ parseCommand(cmd); if (cmdN == ADDSUB){ AddSubCmd a = new AddSubCmd(u,cmdA); } }}21Collaboration Diagram – URS Add Subject Scenarioclass abstract Command { protected String cmd; protected URSDatabase u; public abstract void execute();} class AddSubCmd extends Command{ public AddSubCmd(URSDatabase urs, String cmd){ u = urs; // parse command and set the arguments } public void execute(){ // implement here }}22Collaboration Diagram – URS Add Subject Scenariou:URSDatabasea:AddSubCmd<<local>>3: execute()class URSDatabase{ private String cmd; public