Centralized distributed 812017 soen 6461 software

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centralized?distributed?8/1/2017SOEN 6461 Software Design Methodologies 86
System Behavior and UML Sequence DiagramsIt is useful to investigate and define the behavior of the software as a “black box”.System behavior is a description of what the system does(without an explanation of how it does it).Use cases describe how external actors interact with the software system. During this interaction, an actor generates events.A request event initiates an operation upon the system.1/10/2017SOEN 6461 Software Design Methodologies87
System Behaviour and System Sequence Diagrams (SSDs)A sequence diagram is a picture that shows, for a particular scenario of a use case, the events that external actors generate, their order, and possible inter-system events.For a system sequence diagram, all systems are treated as a black box; the diagram places emphasis on events that cross the system boundary from actors to systems.1/10/2017SOEN 6461 Software Design Methodologies88
Essential Course Material 8/1/2017SOEN 6461 Software Design Methodologies 89
Case study 8/1/2017SOEN 6461 Software Design Methodologies 90
SSDs for Process Sale Scenariochange due, receiptmakePayment(amount)total with taxesendSale()description, totaladdLineItem(itemID, quantity)makeNewSale()*[more items]:Cashier:SystemBox may enclose aniteration area.*[…] is an iterationmarker.Return value(s) associatedwith previous message.Return line is optionalif nothing is returned.External actor1/10/2017SOEN 6461 Software Design Methodologies91
SSD and Use Caseschange due, receiptmakePayment(amount)total with taxesendSale()description, totaladdLineItem(itemID, quantity)makeNewSale()*[more items]:Cashier:SystemSimple cash-only Process Sale Scenario1. Customer arrives at a POS checkoutwith goods to purchase.2. Cashier starts a new sale.3. Cashier enters item identifier.4. System records sale line item, andpresents item description, price andrunning total.cashier repeats steps 3-4 untilindicates done.5. System presents total with taxescalculated.1/10/2017SOEN 6461 Software Design Methodologies92
Naming System Events and OperationsThe set of all required system operations is determined by identifying the system events.makeNewSale()addLineItem(itemID, quantity)endSale()makePayment(amount)1/10/2017SOEN 6461 Software Design Methodologies93
Understanding Sequence Diagrams: System Sequence Diagram (SSD)1/10/2017SOEN 6461 Software Design Methodologies94
Detailed Sequence Diagram95
96select function(“unlock"): SystemUser«initiating actor»prompt for the keyenter keyverify keysignal: valid key, lock openopen the lock,turn on the lightTimer«offstage actor»start ("duration“)System Sequence Diagrams considered interactions between the actorsWe already worked with interaction diagrams: System Sequence DiagramsSystem Sequence Diagrams8/1/2017SOEN 6461 Software Design Methodologies
97select function(“unlock"): SystemUser«initiating actor»prompt for the key

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