System Implementation

Transcription

1 MIT- 534 Systems Analysis and Design Software Quality Assurance Quality assurance Software Engineering Lecture 8 System Implementation ดร. สล ล บ ญพราหมณ ส าน กว ชาสารสนเทศศาสตร Software Engineering Institute (SEI) Capability Maturity Model (CMM) Capability Maturity Model Integration (CMMI) Process improvement CMMI tracks an organization's processes, using five maturity layers Gary B. Shelly, Thomas J. Cashman, and Harry J. Rosenblatt Systems Analysis and Design. 7th Ed. Course Technology. 1 2 Overview of Application Development to translate the logical design into program and code modules that will function properly Creation of the System Design The tasks involved in system design produced an overall design and a plan for physical implementation Application Development Steps Module Start by reviewing documentation from prior SDLC phases and creating a set of program designs After the design is created, coding can begin 3 4

2 การเข ยนโปรแกรม Project Management Even a modest-sized project might have hundreds or even thousands of modules Important to set realistic schedules, meet project deadlines, control costs, and maintain quality เป นการแปลง logic ท ออกแบบโดยใช Diagram ต างๆเพ อเข ยนโดยใช ภาษาส งงาน (Programming language) โดยท วไปการเข ยนควรใช format มาตรฐานเพ อท า ให การด แลโปรแกรมท าได ง าย Should use project management tools and techniques 5 6 Structured Application Development Top-down approach Partitioning Modular design Must proceed carefully, with constant input from programmers and IT management to achieve a sound, well-integrated structure Must ensure that integration capability is built into each design and thoroughly tested Structure Charts Structure charts show the program modules and the relationships among them Control module Subordinate modules 7 8

3 Module Library module Data Couple Control Couple Flag A module uses a flag to signal a specific condition or action to another module Structure Charts Condition A condition line indicates that a control module determines which subordinate modules will be invoked, depending on a specific condition Loop A loop indicates that one or more modules are repeated 9 10 Cohesion and Coupling If you need to make a module more cohesive, you can split it into separate units, each of which performs a single function Loosely coupled Tightly coupled Status flag 11 12

4 Structure Chart Examples Drawing a Structure Chart Step 1: Review the DFDs Step 2: Identify Modules and Relationships Step 3: Add Couples, Loops, and Conditions Step 4: Analyze the Structure Chart and the Data Dictionary Other Structured Development Tools Program Flowcharts Pseudocode 15 16

5 Coding Programming Environments Each IT department has its own programming environment and standards Integrated development environments (IDEs) Generating Code Testing Syntax errors Desk checking Logic errors Structured walkthrough, or code review Design walkthrough Can generate editable program code directly from macros, keystrokes, or mouse actions Unit Testing Test data Programmers must test programs that interact with other programs and files individually Stub testing Regardless of who creates the test plan, the project manager or a designated analyst also reviews the final test results Integration Testing Integration testing, or link testing Testing the programs independently does not guarantee that the data passed between them is correct A testing sequence should not move to the integration stage unless it has performed properly in all unit tests 19 20

6 Testing the System Major objectives: Perform a final test of all programs Demonstrate that users can interact with the system successfully Verify that the system will handle all input data properly, both valid and invalid Ensure that the IT staff has the documentation and instructions needed to operate the system properly and that backup and restart capabilities of the system are adequate Verify that all system components are integrated properly and that actual processing situations will be handled correctly Confirm that the information system can handle predicted volumes of data in a timely and efficient manner Documentation System Testing Acceptance tests You should regard thorough testing as a costeffective means of providing a quality product If conflicting views exist, management will decide whether or not to install the system after a full discussion of the options Program Documentation System Documentation Operations Documentation User Documentation Online documentation 23 24

7 Management Approval After system testing is complete, you present the results to management If system testing produced no technical, economical, or operational problems, management determines a schedule for system installation and evaluation System Installation and Evaluation Remaining steps in systems implementation: Prepare a separate operational and test environment Provide training for users, managers, and IT staff Perform data conversion and system changeover Carry out post-implementation evaluation of the system Present a final report to management

8 Operational and Test Environments The environment for the actual system operation is called the operational environment or production environment The environment that analysts and programmers use to develop and maintain programs is called the test environment A separate test environment is necessary to maintain system security and integrity and protect the operational environment Training Training Plan The first step is to identify who should receive training and what training is needed The three main groups for training are users, managers, and IT staff You must determine how the company will provide training 31 32

9 Train people in groups, with separate training programs for distinct groups Select the most effective place to conduct the training Provide for learning by hearing, seeing, and doing Prepare effective training materials, including interactive tutorials Tutorial Vendor Training If the system includes the purchase of software or hardware, then vendor-supplied training is one of the features you should include in the RFPs (requests for proposal) and RFQs (requests for quotation) that you send to potential vendors Often gives the best return on your training dollars Outside Training Resources Many training consultants, institutes, and firms are available that provide either standardized or customized training packages You can contact a training provider and obtain references from clients Center for the Application of Information Technologies (CAIT) In-House Training The IT staff and user departments often share responsibility When developing a training program, you should keep the following guidelines in mind: Rely on previous trainees Train-the-trainer strategy When Training is complete, many organizations conduct a full-scale test, or simulation 35 36

10 Data Conversion Data Conversion Strategies The old system might be capable of exporting data in an acceptable format for the new system or in a standard format such as ASCII or ODBC If a standard format is not available, you must develop a program to extract the data and convert it Often requires additional data items, which might require manual entry Data Conversion Security and Controls You must ensure that all system control measures are in place and operational to protect data from unauthorized access and to help prevent erroneous input Some errors will occur It is essential that the new system be loaded with accurate, error-free data System Changeover Direct Cutover Involves more risk than other changeover methods Companies often choose the direct cutover method for implementing commercial software packages Cyclical information systems usually are converted using the direct cutover method at the beginning of a quarter, calendar year, or fiscal year 39 Parallel Operation Easier to verify that the new system is working properly under parallel operation than under direct cutover Running both systems might place a burden on the operating environment and cause processing delay Is not practical if the old and new systems are incompatible technically Also is inappropriate when the two systems perform different functions 40

11 Direct and Parallel installation Pilot Operation The group that uses the new system first is called the pilot site The old system continues to operate for the entire organization After the system proves successful at the pilot site, it is implemented in the rest of the organization, usually using the direct cutover method 41 Is a combination of parallel operation and direct cutover methods 42 Phased Operation You give a part of the system to all users The risk of errors or failures is limited to the implemented module only Is less expensive than full parallel operation Is not possible, however, if the system cannot be separated easily into logical modules or segments 43 44

12 Post-Implementation Tasks Post-Implementation Evaluation Includes feedback for the following areas: Accuracy, completeness, and timeliness of information system output User satisfaction System reliability and maintainability Adequacy of system controls and security measures Hardware efficiency and platform performance Effectiveness of database implementation Performance of the IT team Post-Implementation Tasks Completeness and quality of documentation Quality and effectiveness of training Accuracy of cost-benefit estimates and development schedules Post-Implementation Evaluation When evaluating a system, you should: Interview members of management and key users Observe users and computer operations personnel actually working with the new information system Read all documentation and training materials Examine all source documents, output reports, and screen displays 47 48

13 Use questionnaires to gather information and opinions form a large number of users Analyze maintenance and help desk logs Post-Implementation Evaluation Users can forget details of the developmental effort if too much time elapses Pressure to finish the project sooner usually results in an earlier evaluation in order to allow the IT department to move on to other tasks Ideally, conducting a post-implementation evaluation should be standard practice for all information systems projects Final Report to Management Your report should include the following: Final versions of all system documentation Planned modifications and enhancements to the system that have been identified Recap of all systems development costs and schedules A comparison of actual costs and schedules to the original estimates Post-implementation evaluation, if it has been performed Marks the end of systems development work 51