安徽工業(yè)大學(xué) 軟件工程 方木云 ch8

1、Software Prototyping原型法,Rapid software development to validate requirements 快速原型開發(fā)以驗(yàn)證需求,Objectives教學(xué)目的,To describe the use of prototypes in different types of development projectTo discuss evolutionary and throw

2、-away prototypingTo explain the need for user interface prototyping,Topics covered主要內(nèi)容,Prototyping in the software processPrototyping techniquesUser interface prototyping,System prototyping系統(tǒng)原型,Prototyping is the ra

3、pid development of a systemIn the past, the developed system was normally thought of as inferior in some way to the required system so further development was requiredNow, the boundary between prototyping and normal sy

4、stem development is blurred and many systems are developed using an evolutionary approach,Uses of system prototypes系統(tǒng)原型的使用,The principal use is to help customers and developers understand the requirements for the system

5、 幫助用戶和開發(fā)者理解需求Prototyping can be considered as a risk reduction activity which reduces requirements risks 降低風(fēng)險,Prototyping benefits原型法的好處,Misunderstandings between software users and developers

6、 are exposedMissing services may be detected and confusing services may be identifiedA working system is available early in the processThe prototype may serve as a basis for deriving a system specificationThe system

7、can support user training and system testing,Prototyping benefits原型法的好處,Improved system usabilityCloser match to the system neededImproved design qualityImproved maintainabilityReduced overall development effort,Pro

8、totyping in the software process快速原型的類型,1. Evolutionary prototyping 進(jìn)化式An approach to system development where an initial prototype is produced and refined through a number of stages to the final system2. Throw-away

9、prototyping 拋棄式A prototype which is usually a practical implementation of the system is produced to help discover requirements problems and then discarded. The system is then developed using some other development proc

10、ess,Prototyping objectives原型法目標(biāo),The objective of evolutionary prototyping is to deliver a working system to end-users. The development starts with those requirements which are best understood.The objective of throw-awa

11、y prototyping is to validate or derive the system requirements. The prototyping process starts with those requirements which are poorly understood,Evolutionary prototyping進(jìn)化型,Must be used for systems where the specifica

12、tion cannot be developed in advance e.g. AI systems and user interface systemsBased on techniques which allow rapid system iterationsVerification is impossible as there is no specification. Validation means demonstrati

13、ng the adequacy of the system,Evolutionary prototyping,Evolutionary prototyping advantages進(jìn)化型的優(yōu)點(diǎn),Accelerated delivery of the system 加速Rapid delivery and deployment are sometimes more important than functionality or lo

14、ng-term software maintainabilityUser engagement with the system 用戶參與Not only is the system more likely to meet user requirements, they are more likely to commit to the use of the system,Evolutionary prototyping proble

15、ms進(jìn)化型問題,Management problems 管理問題Maintenance problems 維護(hù)問題Contractual problems 合同問題,Prototypes as specifications規(guī)格描述,Some parts of the requirements (e.g. safety-critic

16、al functions) may be impossible to prototype and so don’t appear in the specificationAn implementation has no legal standing as a contractNon-functional requirements cannot be adequately tested in a system prototype,Th

17、row-away prototyping拋棄式原型,Used to reduce requirements riskThe prototype is developed from an initial specification, delivered for experiment then discardedThe throw-away prototype should NOT be considered as a final s

18、ystemSome system characteristics may have been left outThere is no specification for long-term maintenanceThe system will be poorly structured and difficult to maintain,Throw-away prototyping拋棄式原型,,Prototyping with r

19、euse復(fù)用技術(shù),Application level developmentEntire application systems are integrated with the prototype so that their functionality can be sharedFor example, if text preparation is required, a standard word processor can b

20、e usedComponent level developmentIndividual components are integrated within a standard framework to implement the systemFrame work can be a scripting language or an integration framework such as CORBA,Reusable compon

21、ent composition重用構(gòu)件的組成,Visual programming可視化編程,Scripting languages such as Visual Basic support visual programming where the prototype is developed by creating a user interface from standard items and associating compo

22、nents with these itemsA large library of components exists to support this type of developmentThese may be tailored to suit the specific application requirements,Key points主要知識點(diǎn),A prototype can be used to give end-use

23、rs a concrete impression of the system’s capabilitiesPrototyping is becoming increasingly used for system development where rapid development is essentialThrow-away prototyping is used to understand the system requirem

24、entsIn evolutionary prototyping, the system is developed by evolving an initial version to the final version,Key points主要知識點(diǎn),Rapid development of prototypes is essential. This may require leaving out functionality or r

25、elaxing non-functional constraintsPrototyping is essential for parts of the system such as the user interface which cannot be effectively pre-specified. Users must be involved in prototype evaluation,Home work,1 what ar

26、e the four symbols in the DFD? 2 what is the UML? 3 what are the nine type of diagrams in UML?4 what are the disadvantages of DFD? 5What is the software prototyping?6 what are the two types of software prototyping