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UML SIG UML Lecture SeriesRequirements ModelingUML SIGUML Lecture SeriesUML SIGRequirements Modeling(Use Case Diagram+Use Case Description)UML Lecture SeriesRequirements Modeling(Use Case Diagram+Use Case Description)UML SIG UML Lecture SeriesRequirements ModelingUML SIGSession ObjectivesAt the end of this lecture You will be able to:1.Draw a use case diagram to depict functional2.requirements of a system.2.Expose typical mistakes by students.3.Write use case description for a use case.UML SIG UML Lecture SeriesRequirements ModelingUML SIG use case use case diagram functional requirements non-functional requirements actor include extend use case specification/definition/description flow of events alternate flow of events/alternate pathway exception flow of events/exception pathway basic flow of events/happy pathway non-functional requirements/shadow use casesKeywords used in this lectureUML SIG UML Lecture SeriesRequirements ModelingUML SIGThoughts to Ponder To my knowledge,no other software engineering language construct as significant as use cases has been adopted so quickly and so widely among practitioners.I believe this is because use cases play a role in so many different aspects of software engineering.Ivar JacobsonFounding Father of UML and Creator of Use Case DiagramUML SIG UML Lecture SeriesRequirements ModelingUML SIGFunctional vs.Non-FunctionalRequirements FunctionalNon-FunctionalFunctional requirement are user visible features and aretypically initiated by stakeholders of the system generate report,login,etc.Non-functional requirements are non-visible features and but required for a effective running of an application security,backup,etc.UML SIG UML Lecture SeriesRequirements ModelingUML SIGSession ObjectivesAt the end of this lecture You will be able to:1.Draw a use case diagram to depict functional2.requirements of a system.2.Expose typical mistakes by students.3.Write use case description for a use case.UML SIG UML Lecture SeriesRequirements ModelingUML SIGUse Case DiagramDefinition:A diagram that shows a set of use cases and actors and their relationships.Use cases represent system functionality,the requirements of the system from the users perspective.UML SIG UML Lecture SeriesRequirements ModelingUML SIGNotationsuse case A description of a set of sequences of actions,including variants,that system performs that yields an observable value to an actor.actorThe people or systems that provide or receive information from the system;they are among the stakeholders of a system.includeSpecifies that the source use case explicitly incorporates the behaviour of another use case at a location specified by the sourceextend Specifies that the target use case extends the behaviour of the source.UML SIG UML Lecture SeriesRequirements ModelingUML SIGActorsActorsCould be human beings,other systems,timers and clocks or hardware devices.Actors that stimulate the system and are the initiators of events are called primary actors(active)Actors that only receive stimuli from the system are called secondary actors(passive)UML SIG UML Lecture SeriesRequirements ModelingUML SIGActorsActorsWho/what will be interested in the system?Who/what will want to change the data in the system?Who/what will want to interface with the system?Who/what will want information from the system?UML SIG UML Lecture SeriesRequirements ModelingUML SIGUse Case Diagram Guidelines&Caution1.Use cases should ideally begin with a verb i.e generate 2.report.Use cases should NOT be open ended i.e Register(instead should be named as Register New User)2.Avoid showing communication between actors.3.Actors should be named as singular.i.e student and NOT students.NO names should be used i.e John,Sam,etc.4.Do NOT show behaviour in a use case diagram;instead only depict only system functionality.5.Use case diagram does not show sequence unlike DFDs.UML SIG UML Lecture SeriesRequirements ModelingUML SIGExample Include and ExtendUML SIG UML Lecture SeriesRequirements ModelingUML SIGThe use of include and extend is discouraged simply becausethey add unnecessary complexity to a Use Case diagram.Since the primary purpose of use cases is to show usercentred functionality,the precedence of use cases takeslittle importance.Include and ExtendUML SIG UML Lecture SeriesRequirements ModelingUML SIGQuiz 1UML SIG UML Lecture SeriesRequirements ModelingUML SIGQuiz 2UML SIG UML Lecture SeriesRequirements ModelingUML SIGGranularity of Use CasesAdd referenceRemove referenceSearch for referenceUserList referencesUML SIG UML Lecture SeriesRequirements ModelingUML SIGGranularity of Use CasesManage ReferenceUserGenerally,a use case should embody sufficient levels of granularity without which the use case may not be rendered as useful.UML SIG UML Lecture SeriesRequirements ModelingUML SIGSession ObjectivesAt the end of this lecture You will be able to:1.Draw a use case diagram to depict functional2.requirements of a system.2.Expose typical mistakes by students.3.Write use case description for a use case.UML SIG UML Lecture SeriesRequirements ModelingUML SIGMistake 1UML SIG UML Lecture SeriesRequirements ModelingUML SIGMistake 2UML SIG UML Lecture SeriesRequirements ModelingUML SIGMistake 3UML SIG UML Lecture SeriesRequirements ModelingUML SIGMistake 4UML SIG UML Lecture SeriesRequirements ModelingUML SIGMistake 5UML SIG UML Lecture SeriesRequirements ModelingUML SIG Inventory SystemIn order to generate an invoice a clerk must log in.If a clerk is a first time user,one must have themselves registered.There should be an option for a user to register oneself within the login page.Any user can use the system to view products online.The option of login is also provided when a user views products online.Discussion ExerciseDraw a use case diagram for the scenario below:UML SIG UML Lecture SeriesRequirements ModelingUML SIGExercise-SolutionUML SIG UML Lecture SeriesRequirements ModelingUML SIGSession ObjectivesAt the end of this lecture You will be able to:1.Draw a use case diagram to depict functional2.requirements of a system.2.Expose typical mistakes by students.3.Write use case description for a use case.UML SIG UML Lecture SeriesRequirements ModelingUML SIGUse Case SpecificationUML SIG UML Lecture SeriesRequirements ModelingUML SIGUse Case SpecificationUML SIG UML Lecture SeriesRequirements ModelingUML SIGUse Case SpecificationUse case specification is synonymous to use case description and use case definition and can used interchangeably.Use case specification defines information that pertains to a particular use case which is important in understanding the purpose behind the use case.Use case specification is written for every use case.A use case specification has one or more flow of events or pathways association with it.UML SIG UML Lecture SeriesRequirements ModelingUML SIGFlow of Events/PathwaysA flow of events or pathway is a textual description embodying sequence of events with regards to the use case and is part of the use case specification.Flow of events is understood by the customer.A detailed description is necessary so that one can better understand the complexity that might be involved in realising the use cases.UML SIG UML Lecture SeriesRequirements ModelingUML SIGFlow of Events/PathwaysFlow of events describes how and when the use case starts and ends,when the use case interacts with the actors,and the information exchanged between an actor and the use case.Flow of events is derived from a what perspective,NOT how perspective.Hence,specific information like:interface details and technical specifications should NOT be included in a use case description.Use case description serves as a bridge betweenstakeholders of a system and the development team.UML SIG UML Lecture SeriesRequirements ModelingUML SIGFlow of Events/PathwaysUse case description serves as a bridge betweenstakeholders of a system and the development team.Use Case DiagramUse CaseSpecificationProgrammers look at use case specification to understand complete requirements-SRSSystems analyst produce usecase diagram&use case specification in consultation with end usersUML SIG UML Lecture SeriesRequirements ModelingUML SIGFlow of Events/PathwaysFlow of EventsDescribes how and when use casestarts and ends.Does NOT describe user interface details.Is generally a text-based file that is included under its use case in Rational Rose/Visual ParadigmUML SIG UML Lecture SeriesRequirements ModelingUML SIGTypes Flow of Events/PathwaysTypes of Flow of EventsBasic Flow of Events Happy Path-is the most common pathway.It usually depicts a perfect situation,in which nothing goes wrong.Alternate Flow of Events Alternate Pathway -is a pathway that is still considered a good pathway;its just not the most heavily travelled oneException Flow of Events Exception Pathways Unhappy Pathway things dont always go as planned.An exception is an error condition that is important enough to the application to capture.UML SIG UML Lecture SeriesRequirements ModelingUML SIGTypes Flow of Events/PathwaysBasic Flow of Events Happy Path You get to the ATM and successfully withdraw money Alternate Flow of Events Alternate Pathway -You get to the ATM but could not withdraw money due to insufficient funds in your account.Exception Flow of Events Exception Pathways Unhappy Pathway You get to the ATM machine but your valid pin number is not accepted.UML SIG UML Lecture SeriesRequirements ModelingUML SIGSee Example Word Document on Use Case Specification based on Remulak ProductionsUse Case Specifications-ExampleUML SIG UML Lecture SeriesRequirements ModelingUML SIGReview QuestionsUML SIG UML Lecture SeriesRequirements ModelingUML SIGA use case specification cannot be done for an included use case.TrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGUse case specification together with a use case diagram become part of what is know as system requirements specification(SRS)TrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGAlthough non-functional requirements(i.e shadow use cases)are not“technically speaking a use case,are still considered a use case to acknowledge the importance it has in the overall system.TrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGBasic Flow of Events Happy Path is a series of events that happens some of the timeTrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGAlternate Flow of Events Alternate Pathway is a series of events that happens all the timeTrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGException Flow of Events Exception Pathway is a series of events that is impossible to happen.TrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGBoth use case diagram and use case specification should not be too detailed.TrueFalseReview QuestionUML SIG UML Lecture SeriesRequirements ModelingUML SIGUse Case Diagram-In Class ExerciseWrite use case specification based on the case diagram for Inventory System.UML SIG UML Lecture SeriesRequirements ModelingUML SIGSummary1.Use Case Diagram as a means to model functional requirements of a system.2.Awareness of typical mistakes by students.3.Write use case description for a use case.UML SIG UML Lecture SeriesRequirements ModelingUML SIGFurther ReadingUse Case FAQsUML SIG UML Lecture SeriesRequirements ModelingUML SIGReferenceJacobson I.2003,“Use Case Yesterday,Today and Tomorrow,The Rational Edge,IBM
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