System sequence diagram (SSD) Describes flow of information Identifies interaction between actors and system Message oriented The System Sequence Diagram-Identifying Inputs and Outputs In the object-oriented approach, the flow of information is achieved through sending messages either to and from actors or back and forth between internal objects. © Sheridan CollegeĢ4 Identifying Inputs and Outputs-the System Sequence Diagram Scan End of shift/Close Register The next step is to check each of these against each event to confirm that the transitions are correct. List all of the Events and Event on the diagram that can trigger a change in state. How many different state can the POS be in? Logging in Waiting Scanning Charging Logging out Second. Look for additional transitions Expand each transition as appropriate Review and test each statechart © Sheridan CollegeĢ2 Review Exercise – POS (model of the state of a Point of Sale device)įirst. Select the classes that will require statecharts List all the status conditions for each group Specify transitions that cause object to leave the identified state Sequence state-transition combinations in correct order © Sheridan CollegeĢ1 Rules for Developing Statecharts (continued) © Sheridan CollegeĢ0 Summarize: Rules for Developing Statecharts Ensure that no states are unreachable or unleavable. You have found a bug! © Sheridan Collegeġ9 State Tables To design a set of functional tests from a state transition diagram, the rules are simple: Visit every state. If you find a combination of state, event, and condition for which the attendant action and subsequent state are not specified, congratulations. You can then specify the correct action or next state. A state table overcomes that limitation by combining every known state with every event combination that can occur. Often they overlook things that can’t or shouldn’t happen. Ready to Scan next Order © Sheridan Collegeġ8 State Tables State Transition Diagrams often don’t show all possible combinations of states and events. Login Screen User: PW: © Sheridan College © Sheridan Collegeġ0 Here’s a simple example State Transition Diagram for a washing machine.ġ1 Typical Washing Machine User Interfaceġ2 A condition is typically some kind of event, e.g.: SignalĪrrival of an object (data/material), Etc… An action is the appropriate output or response to the event, e.g.: Signal or message Transfer of an object, Calculation, Etc… Condition Action © Sheridan Collegeġ3 Something we might be more familiar with! Transition: (Virtually) instantaneous change in state (behavior). A state is when a system is: Doing something – e.g., heating oven, mixing ingredients, accelerating engine, Waiting for something to happen – Waiting for user to enter password, waiting for sensor reading. State: Some behavior of a system that is observable and that lasts for some period of time. From a business perspective, tracking the state of an object provides users with important status information on key elements. What is a State Diagram? Purpose: To model the various states that a system, user, or object can be in, including initial and final states. I-C-E-06 Two ways of modelling Summarize Requirements Gathering Process Car Rental System – Case Study Introduce System Sequence Diagrams (SSDs) Quiz No 2 ICE-07 © Sheridan CollegeĤ Typical Amazon Package Tracking Status Reportĥ Review I-C-E-06 Two Versions – check SLATE © Sheridan College 1 State Diagrams / System Sequence Diagrams (SSDs)Ģ Agenda Weekly Schedule-SLATE Solutions to ICE’s posted on SLATE TodayĪssignment No 2 Rubric Posted Quiz No 3 next week Solutions to ICE’s posted on SLATE Today State charts – continued.
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