Application architecturesObjectivesTopics coveredGeneric application architecturesUse of application architecturesApplication typesApplication type examplesData processing systemsInput-process-output modelInput-process-outputData-flow diagramsSalary payment DFDTransaction processing systemsTransaction processingATM system organisationTransaction processing middlewareTransaction managementInformation systems architectureInformation system structureLIBSYS architectureLIBSYS organisationResource allocation systemsResource allocation architectureLayered resource allocationLayered system implementationE-commerce system architectureEvent processing systemsEditing systemsEditing system componentsEditing system architectureLanguage processing systemsA language processing systemLanguage processing componentsData-flow model of a compilerRepository model of a compilerKey pointsSlide 37©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 1Application architectures©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 2ObjectivesTo explain the organisation of two fundamental models of business systems - batch processing and transaction processing systemsTo describe the abstract architecture of resource management systemsTo explain how generic editors are event processing systemsTo describe the structure of language processing systems©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 3Topics coveredData processing systemsTransaction processing systemsEvent processing systemsLanguage processing systems©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 4Generic application architecturesApplication systems are designed to meet an organisational need.As businesses have much in common, their application systems also tend to have a common architecture that reflects the application requirements.A generic architecture is configured and adapted to create a system that meets specific requirements.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 5Use of application architecturesAs a starting point for architectural design.As a design checklist.As a way of organising the work of the development team.As a means of assessing components for reuse.As a vocabulary for talking about application types.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 6Application typesData processing applications•Data driven applications that process data in batches without explicit user intervention during the processing.Transaction processing applications•Data-centred applications that process user requests and update information in a system database.Event processing systems•Applications where system actions depend on interpreting events from the system’s environment.Language processing systems•Applications where the users’ intentions are specified in a formal language that is processed and interpreted by the system.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 7Application type examplesData processing systems•Billing systems;•Payroll systems.Transaction processing systems•E-commerce systems;•Reservation systems.Event processing systems•Word processors;•Real-time systems.Language processing systems•Compilers;•Command interpreters.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 8Data processing systemsSystems that are data-centred where the databases used are usually orders of magnitude larger than the software itself.Data is input and output in batches•Input: A set of customer numbers and associated readings of an electricity meter;•Output: A corresponding set of bills, one for each customer number.Data processing systems usually have an input-process-output structure.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 9Input-process-output modelSystemInput Process OutputPrinterDatabase©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 10Input-process-outputThe input component reads data from a file or database, checks its validity and queues the valid data for processing.The process component takes a transaction from the queue (input), performs computations and creates a new record with the results of the computation.The output component reads these records, formats them accordingly and writes them to the database or sends them to a printer.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 11Data-flow diagramsShow how data is processed as it moves through a system.Transformations are represented as round-edged rectangles, data-flows as arrows between them and files/data stores as rectangles.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 12Salary payment DFDRead employeerecordRead monthlypay dataComputesalaryWrite taxtransactionsMonthly paydataTaxtablesTaxtransactionsPension dataValidateemployee dataWrite pensiondataWrite banktransactionWrite socialsecurity dataEmployeerecordsMonthly payratesBanktransactionsSocial securitydataPrint payslipPRINTERDecodedemployeerecordPay informationValidemployee recordTax deduction + SSnumber + tax offi cePensiondeduction +SS numberEmpoyee data+ deductionsNet payment + bankaccount info.Social securitydeduction + SS number©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 13Transaction processing systemsProcess user requests for information from a database or requests to update the database.From a user perspective a transaction is:•Any coherent sequence of operations that satisfies a goal;•For example - find the times of flights from London to Paris.Users make asynchronous requests for service which are then processed by a transaction manager.©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 14Transaction processingI/OprocessingApplicationlogicTransactionmanagerDatabase©Ian Sommerville 2006 Software Engineering, 8th edition. Chapter 13 Slide 15ATM system organisationGet customeraccount idValidate cardInputQuery accountUpdate accountPrint detailsReturn cardDispense cashProcessOutputSelect