Use Cases and ScenariosWe Will CoverWhat is a Use-CaseUser Goals versus User InteractionsGoals and InteractionsUse-Case Diagrams (POST)Another ExampleIncludes and ExtendsSetting the System BoundaryA Different BoundaryEmbedded System “Onion Skin”Partial POSTPOST Use-CasePOST Expanded Use-CaseThe Home Heating SystemHome Heating Use-Case DiagramHome Heating Use-CasesModified Home HeatingModified: Home Heating Use-CasesSlide 23HACSHACS Use-Case DiagramHACS Use-CasesAlternate HACSAlternate HACS Use-CasesWhen to use Use-CasesHow it Fits TogetherUse Cases and ScenariosUse Cases and ScenariosWe Will CoverWe Will CoverWhat is a use-caseUse-case versus user interactionUse-Case diagramsThe constructs in the use-case diagramsCapturing the use-case High-level use-caseExtended use-caseDifference between use case and scenarioWhat is a Use-CaseWhat is a Use-CaseA use-case captures some user visible functionThis may be a large or small functionDepends on the level of detail in your modeling effortA use-case achieves a discrete goal for the userExamplesFormat a documentRequest an elevatorHow are the use cases found (captured or elicited)?User Goals versus User InteractionsUser Goals versus User InteractionsConsider the following when formatting a documentDefine a styleChange a styleCopy a style from one document to the nextversusFormat a documentEnsure consistent formatting of two documentsThe latter is a user goalSomething the user wants to achieveThe former are user interactionsThings the user does to the system to achieve the goalGoals and InteractionsGoals and InteractionsThere is a place for both goals and interactionsUnderstand what the system shall doCapture the user goalsUnderstand how the user will achieve the goalsCapture user interactionsSequences of user interactionsThus, start with the user goals and then refine the user goals into several (many) user interactionsUse-Case Diagrams (POST)Use-Case Diagrams (POST)CustomerCashierBuy ItemLog InRefund a Purchased ItemPOSTUse CaseSystem BoundaryAdapted from Larman “Applying UML and Patterns”POST: Point of Sale TerminalSalespersonTraderAccounting SystemTrading ManagerSet LimitsUpdate AccountsAnalyze RiskPrice DealCapture DealLimit ExceededValuation«includes»«includes»«extends»Another ExampleAnother ExampleAdapted from Fowler “UML Distilled”Includes and ExtendsIncludes and ExtendsIncludesYou have a piece of behavior that is similar across many use casesBreak this out as a separate use-case and let the other ones “include” itExamples includeValuationValidate user interactionSanity check on sensor inputsCheck for proper authorizationExtendsA use-case is similar to another one but does a little bit morePut the normal behavior in one use-case and the exceptional behavior somewhere elseCapture the normal behaviorTry to figure out what can go wrong in each stepCapture the exceptional cases in separate use-casesMakes it a lot easier to understandC u s t o m e rC a s h i e rB u y I t e mL o g I nR e f u n d a P u r c h a s e d I t e mP O S TM HSetting the System BoundarySetting the System BoundaryThe system boundary will affect your actors and use-casesAdapted from Larman “Applying UML and Patterns”CustomerBuy ItemRefund a Purchased ItemStoreA Different BoundaryA Different BoundaryLet us view the whole store as our systemAdapted from Larman “Applying UML and Patterns”Embedded System “Onion Skin”Embedded System “Onion Skin”Perception/ActionSensors/ActuatorsSystemInterfaces*Partial POSTPartial POSTC u s t o m e rC a s h i e rB u y I t e mL o g I nR e f u n d a P u r c h a s e d I t e mP O S TS t a r t U pM a n a g e U s e r sA n d a L o t M o r eM a n a g e rS y s t e m A d m i n i s t r a t o rM HAdapted from Larman “Applying UML and Patterns”POST Use-CasePOST Use-CaseUse case: Buy ItemActors: Customer (initiator), CashierType: PrimaryDescription: The Customer arrives at thecheckout with items to purchase.The Cashier records the purchaseitems and collects a payment.On completion the Customerleaves with the itemsPOST Expanded Use-CasePOST Expanded Use-CaseUse case: Buy ItemActors: Customer (initiator), CashierType: Primary and essentialDescription: The Customer arrives at the checkout with items to purchase. The Cashier records the purchaseitems and collects a payment. On completion the Customer leaves with the items.Cross Ref.: Requirements XX, YY, and ZZUse-Cases: Cashier must have completed the Log In use-caseFuel Valve9080706050OnOffControllerBurnerWater PumpHot WaterFuelTemp SensorWater ValveControl PanelHomeThe Home Heating SystemThe Home Heating SystemTemp Sensor*Home Heating Use-Case DiagramHome Heating Use-Case DiagramH o m e O w n e rM HP o w e r U pP o w e r D o w nC h a n g e T e m p .H o m e H e a t i n gHome Heating Use-CasesHome Heating Use-CasesUse case: Power UpActors: Home Owner (initiator)Type: Primary and essentialDescription: The Home Owner turns the power on. Each roomis temperature checked. If a room is below thethe desired temperature the valve for the room is opened, the water pump started. If the water temp falls below threshold, the fuel valve isopened, and the burner ignited. If the temperature in all rooms is above the desiredtemperature, no actions are taken. Cross Ref.: Requirements XX, YY, and ZZUse-Cases: NoneModified Home HeatingModified Home HeatingHome OwnerMHPower UpPower DownChange Temp.Home HeatingAdjust TempTemp. HighTemp. Low«includes»«includes»«includes»«includes»Modified:Home Heating Use-CasesModified:Home Heating Use-CasesUse case: Power UpActors: Home Owner (initiator)Type: Primary and essentialDescription: The Home Owner turns the power on. Perform Adjust Temp. If the temperature in all rooms isabove the desired temperature, no actions are taken. Cross Ref.: Requirements XX, YY, and ZZUse-Cases: Perform Adjust Temp*Modified:Home Heating Use-CasesModified:Home Heating Use-CasesUse case: Adjust TempActors: System (initiator)Type: Secondary and essentialDescription: Check the temperature in each room. For each room below target, open room valve, start pumpif not started. If water temp falls below threshold,open fuel value and ignite burner.Cross Ref.: Requirements XX, YY, and ZZUse-Cases: