软件工程第4讲

1.6 S.E. Tasks and ResearchContent1.6.1 Software Characteristicsis not manufactured evidently Softwaredoesn’t “wear out”is decomposable and expansible1.6.2 Software Development difficulties①Productivity: Low;②Reliability: Low;③Maintainability: Low;④Management: Difficult;⑤Cost: High.Boehm:Software engineering is used as m o d er n s c i e n c e t e c h n o l o g y knowledge to design,construct c o m p u t e r p r o g r a m ,a n d essential relative documents in development,operation and m a i n t e n a n c e t h e p r o g r a m.1) Software Engineering Definition 1.6.3 Software Engineering FrameIEEE (p19):Software engineering :(1)The application of a systematic,d i s c i p l i ne d,q u a n t if i a b l eapproach to the development,operation,and maintenance ofsoftware;that is,the applicationof engineering to software.(2)The study of approaches as in(1).Webster:Software engineering is application of science and mathematics,through which,making up computer devices abilities with the aid of computer p r o g r a m,p r o c e s s a n d r e l a t i v e documents into useful thing for human.Fairley:Software engineering is the systematic development and maintenance technology and management subject that enable a software product to be developed and corrected at the limited cost on time.Frith Bauer (p18):Software engineering is the establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines.R.S.Pressman (p1):The technology encompasses a process, a set of methods, and an array of tools that we call software engineering.Software Engineering A Layered Technology Software Engineering a “quality” focusprocess modelmethodstoolsGoals of SEImprove the productivity of the development process Improve the comprehension of the developed software systems Improve the quality of the software product at all levels ReliabilityEfficiency (Speed, resource usage)User-friendly (user acceptance)Maintainability (comprehensive design and documentation) General goal:to produce quality software which is economic and useful and safe for people.Concerns of SEProductsSoftware products, test drivers (internal and external)Paper documents (internal and external)ProcessesHow software is created (plan, tools, techniques)How the quality is evaluated and ensuredToolsCASE tools, editors, project management tools, etc.PeopleTechnical, social, and managerial skillsPrinciplesProviding repeatability, guidelines and maturity in the software development process2) Software Engineering FramePrinciplesSupport ValidateCodeDesignAnalyzeSelect appropriate development modelAdopt appropriate design methodProvide high quality engineering supportPay attention to development process managementUsability CorrectnessWorthiness12A Common Process FrameworkCommon process frameworkFramework activitieswork taskswork productsmilestones & deliverablesQA checkpointsUmbrella ActivitiesUmbrella ActivitiesSoftware project managementFormal technical reviewsSoftware quality assuranceSoftware configuration management Document preparation and production Reusability managementMeasurementRisk management2) Software engineering methodologySoftware Engineering TheoryStructureMethodsToolsbaseLink,Promote each other1) Software normalization and standard 1.6.4 Research Content and MethodsRepresentationFormalInformal DefinitionStructured declaration Documentation3) Software tools and support environment①Software toolSoftware tool is a set of programs that aid to develop,test,analyze,maintain o t h e r c o m p u t e r p r o g r a m s a n d documents,to implement automatization of software product process,to improve the software productivity,reliability,and to reduce the software product cost.Requirements analysis tools Array Design toolsSoftware toolsCoding toolsValidation toolsMaintenance toolsⅠ) What’s the software environment Software environment is defined as a set of tools that are effective for entire software life cycle.Ⅱ) Software environment iscomposed of databasea set of tools call mode②Software support environmentⅢ) Characteristics①tightness②firmness③adaptability④portability4）Software project management Plan managementCost managementQuality managementOrganization managementExercisesTranslate the following definitions in to Chinese:(1)Software engineering is the discipline concerned with the application of theory,knowledge,and practice for effectively and efficiently building software system that satisfies the requirements of users and customers.S.E.is applicable to small,medium,and large-scale system.It encompasses all phases of the life cycle of a software system.S.E.employs engineering methods,processes,techniques,and measurement.It benefits from the use of tools for managing software development;analyzing and modeling software artifacts;assessing and controlling quality;and for ensuring a disciplined,controlled approach to software evolution and reuse.The elements of software engineering are applicable to the development of software in any computing application domain where professionalism,quality,schedule and cost are important in producing software system.(2)An international set of standards that can be used in the development of a quality management system in all industries is called ISO9000.ISO9000standards can be applied to a range of organizations from manufacturing to service industries.ISO 9001is the most general of these standards and applies to organizations concerned with the quality process in organizations that design,develop and maintain products.A supporting document(ISO9000-3)interprets ISO9001for software development.Several books describing the ISO9001standard are available(Johnson,1993;Oskarsson andGlass,1995;Peach,1996;Bamford and Deibler,2003).The ISO9001standard isn’t specifically aimed at software development but sets out general principles that can be applied to software.The ISO9001standard describes various aspects of the quality process and lays out the organizational standards and procedures that a company should define.These should be documented in an organizational quality manual.The process definition should include descriptions o f t h e d o c u m e n t a t i o n r e q u i r e d t o demonstrate that the defined processes have been followed during product development.（3）Software engineering is an engineering discipline whose focus is the cost-effective development of high-quality software systems.Software is abstract and intangible. It is not constrained by materials，or g o v e r n e d b y p h y s i c a l l a w s o r b y manufacturing processes.In some ways，this simplifies software engineering as there are no physical limitations on the potential of software.However,this lack of natural constraints means that software can easily become extremely complex and hence very difficult to understand.Chapter 2 Software Project Planningcustomerplannerplansystem specificationNeed ……,Want ……,Wehave ……What?Who?When?How many?TasksSoftware scopeResourcesSoftware Cost EstimationSoftware Project Scheduling2.1 Software scopeFunctions Performance Constraints Interfaces Reliability Describe in some languageSoftware scopeUnderstandableplannerSoftware scope1.Functions:the more detail we describe, the better we get the functions description;2.Performance:must be considered with functions simultaneously,because the same function can precipitate an order of magnitude difference in development effort when considered in the context of different performance bounds;3.Constraints:identify limits placed on the softwareby external hardware,available memory or other existing systems.Constraints must be evaluated together with functions and performance;4.Interfaces:hardware,software,people andprocedures;5.Reliability:we can use the nature of the project to aid in describing the software reliability.(1)hardware (e.g., processor, peripherals) that executes the software and devices (e.g., machines，displays) that are indirectly controlled by the software；(2)software that already exists (e.g., databaseaccess routines，reusable software components, operating system) and must be linked to the new software；(3)people who make use of the software via keyboard, mouse or other I/O devices, and(4)procedures that precede or succeed the software as a sequential series of operations．In each case the information transfer across the interface mustbe clearly understood.See you next!。