第2章系统开发战略与方法.ppt

1、Management Information System,Zhao Ping Tianjin Agricultural University February 28,2008,Chapter 2 Developing strategy and methods of MIS,Contents: 2.1 Cognizable developing model of MIS 2.2 Systems development life cycle of MIS 2.3 Developing strategy and methods of MIS 2.4 People and developing fa

2、shion,Developing requirement of MIS,管理信息系统的开发是指管理信息系统从问题提出开始，从系统调查规划、系统分析、设计、实施，到系统维护、评价的全过程。 现行系统可能是一个手工系统，也可能是以前投入运行的、但是已经无法满足企业运作、管理需要的管理信息系统。,2.1Cognizable process of the development,认知过程 管理信息系统的开发者面临的最大的问题在于如何准确、完整地获得用户的需求，而大多数系统的开发者不可能是一个业务专家，对相关问题有充分的认识，因此在管理信息系统的开发中有一个认知过程。,Development proce

3、ss of MIS,就是根据需要解决的问题，建立一个有信息技术支撑、与解决问题相关的、数据处理的、可运行的计算机模型。,real-life： problem,computer world： computer-executed model,观念世界 逻辑模型,数据世界 物理模型,计算机世界 计算机可 执行模型,现实世界：问题,认知模型,问题域:某个信息系统所要处理的问题所涉及的领域（范围）称为问题域（问题空间） 逻辑模型：识别用户需求，确定开发系统的功能（“作什么？”） 物理模型：在一定信息技术、系统平台约束下，设计系统实现方式（“如何做？”） 计算机可执行模型：利用计算机语言设计出相应的计算机

4、程序。, 2.2 the systems development life cycle, 2.2 the systems development life cycle,the systems development life cycle,The SDLC is a structured step-by-step approach for developing information systems. There are literally hundreds of different activities associated with each phase in the SDLC. Typic

5、al activities include determining budgets, gathering business requirements, designing models, and writing detailed user documentation.,the SDLC and associated activities,Phase1:Planning,Define the system to be developed You must identify and select the system for development or determine which syste

6、m is required to support the strategic goals of your organization. Organization typically track all the proposed systems and prioritize them based on business impact or critical success factors. CSF is a factor critical to your organizations success.,Phase1:Planning(Cont.),Set the project scope You

7、must define the projects scope and create a project scope document for your systems development effort. The project scope clearly defines the high-level system requirement. Scope is often referred to the most basic definition of the system. Setting the project scope is important for if helps you avo

8、id scope creep and feature creep.,Phase1:Planning(Cont.),Scope creep Scope creep occurs when the scope of the project increases beyond its original intentions. Feature creep Feature creep occurs when developers add extra features that were not part of the initial requirements. project scope document

9、 A project scope document is a written definition of the project scope and is usually no longer than a paragraph.,Phase1:Planning(Cont.),Develop the project plan You must develop a detailed project plan for your entire systems development effort. The project plan defines the what, when, and who ques

10、tions of systems development including all activities to be performed, the individuals, or resources, who will perform the activities, and the rime required to complete each activity. The detailed project plan is the guiding force behind ensuring the on-time delivery of a complete and successful inf

11、ormation system.,Phase2:Analysis,The analysis phase of SDLC involves end-users and IT specialists working together to gather, understand, and document the business requirements for the proposed system. The following are the two primary activities youll perform during the analysis phase: Gathering th

12、e business requirements Prioritize the requirements,Gathering the business requirements,Business requirements are the detailed set of employee requests that the system must meet to be successful. The business requirements drive the entire system. An extremely useful way to gather business requiremen

13、ts is to perform a joint application development (JAD) session. During a JAD session, users and IT specialists meet, sometimes for several days, to define and review the business requirements for the system.,Prioritize the requirements,Once you define all the business requirements, you prioritize th

14、em in order of business importance and place them in a formal comprehensive document, the requirements definition document (RDD). The users receive the RDD for their sign-off. Sign-off is the users actual signatures indicating they approve all the business requirements. Typically, one of the first m

15、ajor milestones in the project plan is the users sign-off on business requirements.,the cost of finding errors,One of the key things to think about when you are reviewing business requirements is the cost to the company of fixing errors if the business requirements are unclear or inaccurate. An erro

16、r found during the analysis phase is relatively inexpensive to fix; all you typically have to do is change a Word document. An error found during later phases, however, is incredibly expensive to fix because you have to change the actual system.,Phase 3:Design,The primary goal of the design phase of

17、 the system development lift cycle is to build a technical blueprint of how the proposed system will work. During the analysis phase, end users and IT specialists work together to develop the business requirements for the proposed system from a logical point of view.,Phase 3:Design (Cont.),During an

18、alysis you document business requirements without respect to technology or the technical infrastructure that will support the system. As you move to design, the project team turns its attention to the system from a physical or technical point of view. You take the business requirements generated dur

19、ing the analysis phase and define the supporting technical architecture in the design phase.,1.Design the technical architecture,The technical architecture defines the hardware, software, and telecommunications equipment required to run the system. Most systems run on a computer network with each em

20、ployee having a workstation and the application software running on a server. The telecommunications requirements encompass access to the Internet and the ability for end users to connect remotely to the server. You typically explore several different technical architecture before choosing the final

21、 technical architecture.,2.Design the system model,Modeling is the activity of drawing a graphical representation of a design. You model everything you build including screens, reports, software, and databases. There are many different types of modeling activities performed during the design phase i

22、ncluding a graphical user interface screen design.,Phase 4:Development,During the development phase of the systems development lift cycle, you take all your detailed design documents from the design phase and transform them into an actual system. This phase marks the point at which you go from physi

23、cal design to physical implementation.,two main activities of this phase,1.Build the technical architecture For you to build your system, you must first build the platform on which the system is going to operate. In the development phase, you purchase and implement equipment necessary to support the

24、 technical architecture you designed during the design phase.,two main activities of this phase,2.Build the database and programs Once the technical architecture is built, you initiate and complete the creation of supporting databases and writing the software required for the system. These tasks are

25、 usually undertaken by IT specialists, and it may take months or even years to design and create the databases and write all the software.,Phase 5: Testing,The testing phase of the system development lift cycle verifies that the system works and meets all the business requirements defined in the ana

26、lysis phase. Testing is critical. 1.write the test conditions You must have detailed test conditions to perform an exhaustive test. Test conditions are the detailed steps the system must perform along with the expected results of each step.,1.write the test conditions,The tester will execute each te

27、st condition and compare the expected results with the actual results so verify that the system function correctly. Each time the actual result is different from the expected result, a “bug” is generated, and the system goes back to development for a “bug fix ”. A typical systems development effort

28、has hundreds or thousands of test conditions. You must execute and verify all of these test conditions to ensure the entire system functions correctly.,2.Perform the testing of the system,You must perform many different types of tests when you begin testing your new system. A few of the more common

29、tests include: Unit testing-tests individual units or pieces of code for a system; System testing-verifies that the units or pieces of code written for a system function correctly when integrated into the total system; Integration testing-verifies that separate systems can work together; User accept

30、ance testing(UAT)-determines if the system satisfies the business requirements and enables users to perform their jobs correctly.,Phase 6:Implementation,During the implementation phase of the SDLC you distribute the system to all the users and they begin using the system to perform their everyday jo

31、bs. The following are the two primary activities: 1.Write detailed user documentation When you install the system, you must also provide employees with user documentation that highlights how to use the system. Users find it extremely frustrating to have a new system without documentation.,2.Provide

32、training for the system users,You must also provide training for the users who are going to use the new system. You can provide several different types of training, and two of the most popular are online training and workshop training.,implementation methods,You also need to choose the implementatio

33、n method that best suits your organization, project, and employees to ensure a successful implementation. When you implement the new system, you have four implementation methods: 1.Parallel implementation uses both the old and new systems until youre sure that the new system performs correctly. 2.Pl

34、unge implementation discards the old system completely and immediately uses the new system.,implementation methods (Cont.),3.Pilot implementation has only a small group of people using the new system until you know it works correctly and then the remaining people are added to the system. 4.Phased im

35、plementation installs the new system in phases until youre sure it works correctly and then the remaining phases of the new system are implemented.,Phase 7:Maintenance,Maintaining the system is the final phase of any systems development effort. During the maintenance phase of the SDLC, you monitor a

36、nd support the new system to ensure it continues to meet the business goals. Once a system is in place, it must change as your business changes. Constantly monitoring and supporting the new system involves making minor changes and reviewing the system to be sure that it continues to move your organi

37、zation toward its strategic goals.,two primary activities of maintenance,1.Build a help desk to support the system users One of the best ways to support users is to create a help desk. A help desk is a group of people who respond to users questions. Typically, users have a phone number for the help

38、desk they call whenever they have issues or questions about the system. Provide a help desk that answers user questions is a terrific way to provide comprehensive support for users using new systems.,two primary activities of maintenance,2.Provide an environment to support system changes As changes

39、arise in the business environment, you must react to those changes by assessing their impact on the system. It might well be that the system needs to be adapted or updated to meet the ever-changing needs of the business environment. If so, you must modify the system to support the new business envir

40、onment.,2.3 developing strategy and methods of MIS,Waterfall Methodology The traditional waterfall methodology is a sequential, activity-based process in which one phase in the SDLC is followed by another, from planning through implementation. The waterfall methodology is one of the oldest software

41、development methodologies and has been around for over 30 years.,the software lift cycle,waterfall methodology,Because of the cascade from one phase to another, this model is known as the “waterfall model” or software lift cycle. The principal stages of the model map onto fundamental development act

42、ivities: 1.Requirements analysis and definition The systems services, constraints and goals are established by consultation with system users. They are then defined in detail and serve as a system specification.,2.System and software design,The system design process partitions the requirements to ei

43、ther hardware or software systems. It establishes an overall system architecture. Software design involves identifying and describing the fundamental software system abstractions and their relationships.,3. Implementation and unit testing,During this stage, the software design is realized as a set o

44、f programs or program units. Unit testing involves verifying that each unit meets its specification.,4.Integration and system testing,The individual program units or programs are integrated and tested as a complete system to ensure that the software requirements have been met. After testing, the sof

45、tware system is delivered to the customer.,5. Operation and maintenance,Normally this is the longest lift-cycle phase. The system is installed and put into practical use. Maintenance involves correcting errors which were not discovered in earlier stages of the lift cycle, improving the implementatio

46、n of system units and enhancing the systems services as new requirements are discovered.,the features of waterfall methodology,In principle, the result of each phase is one or more documents which are approved(sign-off). The following phase should not start until the previous phase has finished. In

47、practice, these stages overlap and feed information to each other. During design, problems with requirements are identified, during coding design problems are found and so on. The software process is not a simple linear model but involves a sequence of iterations of the development activities.,water

48、fall methodology,The problem with the waterfall model is its inflexible partitioning of the project into these distinct stages. Commitments must be made at an early stage in the process and this means that it is difficult to respond to changing customer requirements.,waterfall methodology (Cont.),Th

49、erefore, the waterfall model should only be used when the requirements are well understood. However, the waterfall model reflects engineering practice. Consequently, software processes based on this approach are all still used for software development, particularly when this is part of a larger syst

50、ems engineering project.,Rapid application Development Methodology,In response to the pace of the economy, rapid application development has become a popular route for accelerating systems development. The rapid application development(RAD) (also called rapid prototyping) methodology emphasizes exte

51、nsive user involvement in the rapid and evolutionary construction of working prototypes of a system to accelerate the systems development process.,the fundamentals of RAD,Focus initially on creating a prototype ( i.e. a working model) that looks and acts like the desired system. Actively involve sys

52、tem users in the analysis, design, and development phases. Accelerate collecting the business requirements through an interactive and iterative construction approach.,prototype,A prototype is a smaller-scale representation or working model of the users requirements or a proposed design for an inform

53、ation system. The prototype is an essential part of the analysis phase when using the RAD methodology.,Extreme Programming methodology,The extreme programming(XP) methodology breaks a project into tiny phases and developers cannot continue on to the next phase until the current phase is complete. XP

54、 is a significant departure from traditional software development methodologies, and many organizations in different industries have developed successful software using it.,XP,One of the reason for XPs success is that it stresses customer satisfaction. XP empowers (v.授权与, 使能够) developers to respond

55、to changing customer and business requirements, even late in the systems development lift cycle, and emphasizes teamwork. Managers, customers, and developers are all part of a team dedicated to delivering quality software. XP implements a simple, yet effective, way to enable group style development.

56、 The XP methodology supports quickly being able to respond to changing requirements and technology.,Agile methodology,The agile methodology, a form of XP, aims for customer satisfaction through early and continuous delivery of useful software components. Agile is similar to XP but with less focus on

57、 team coding and more on limiting project scope. An agile project sets a minimum number of requirements and turns them into a deliverable product. Agile means what it sounds like: fast and efficient; small and nimble(adj.敏捷的); lower cost; fewer features; shorter projects.,SSA On the other hand, if e

58、nd users develop prototypes to create their own system, they would cycle through steps 3 and 4 until the prototype becomes the final system.,prototyping,Most often, IT specialists develop prototypes using special prototyping development tools. Many of these tools dont support the creation of a final

59、 system-you simply use them to build prototypes. Therefore, the finished prototype becomes a blueprint or technical design for the final system. In the appropriate stages of the SDLC, IT specialists implement the prototype in another application development environment better suited to the development of whole systems.,The advantages of prototyping,1.Encourages active user participation First and foremost ( adj, 最重要的), prototyping encourages users to actively participate in the development process. As opposed to interviewing (面试) and reviewing (评审) documentation, prototyping allows users t