Systems development refers to all the activities that go into producing an information systems solution to an organizational problem or opportunity. Systems development is a structured kind of problem solving with distinct activities consisting of: Show
Figure 13-3
Systems analysis involves defining the problem, identifying its causes, specifying the solution, and identifying the information requirements that must be met by a system solution. System analysis also involves a feasibility study used to determine whether the proposed solution is achievable, from a financial, technical, and organizational standpoint, given the organization's resources and constraints. One of the most challenging task of the systems analyst is to define the specific information requirements that must be met by the system solution selected. Information requirements of a new system involve identifying who needs what information, where, when, and how. The systems design is the overall plan or model that shows how the system will meet its information requirements. Like a blueprint of a building or house, a system design consists of all the specifications that give the system its form and structure. The system designer details the systems specifications that should address all of the managerial, organizational, and technical components of the system solution. User information requirements drive the entire system building effort, so information system design often demands a very high level of end-user participation. During the programming stage, system specifications that were prepared during the design stage are translated into software program code. Thorough testing must be conducted to confirm that the system produces the right results. Testing an information system involves three types of activities:
To ensure that all aspects of testing are as comprehensive as possible, the development team works with users to devise a systematic test plan. Figure 13-4
Conversion is the process of changing from the old system to the new one. There are four main conversion strategies:
Moving from an old system to a new one requires that end users be trained to use the new system. Detailed documentation showing how the system works from both a technical and end-user standpoint is finalized during conversion time for use in training and everyday operations. The production stage is in effect after the system is installed and conversion is complete. The system is reviewed to determine if it meets the original objectives. In some instances, a formal postimplementation audit document is prepared. Changes in hardware, software, documentation, or procedures to a production system to correct errors, meet new requirements, or improve processing efficiency are termed maintenance. Structured methodologies and object-oriented development are the most prominent methodologies for modeling and designing systems. Structured methodologies have been used since the 1970s to document, analyze, and design information systems. Structured development methods are process-oriented, focusing primarily on modeling the processes, or actions that capture, store, manipulate, and distribute data as the data flow through a system. These methods separate data from processes. A separate programming procedure must be written every time someone wants to take an action on a particular piece of data. Tools used in structured development include:
Figure 13-5, Figure 13-6
Object-oriented development uses the object as the basic unit of systems analysis and design. An object combines data and the specific processes that operate on those data. Data encapsulated in an object can be accessed and modified only by the operations, or methods, associated with that object. Instead of passing data to procedures, programs send a message for an object to perform an operation that is already embedded in it. The system is modeled as a collection of objects and the relationships among them. Object-oriented modeling is based on the concepts of class and inheritance. Objects belonging to a certain class, or general categories of similar objects, have the features of that class. Classes of objects in turn can inherit all the structure and behaviors of a more general class and then add variables and behaviors unique to each object. Figure 13-7
The phases of object-oriented development are similar to those of conventional systems development, consisting of analysis, design, and implementation. However, object-oriented development is more iterative and incremental than traditional structured development. In object-oriented development, a system is implemented by translating the design into program code, reusing classes that are already available in a library of reusable software objects and adding new ones created during the object-oriented design phase. Implementation may also involve the creation of an object-oriented database. Because objects are reusable, object-oriented development could potentially reduce the time and cost of writing software because organizations can reuse software objects that have already been created as building blocks for other applications. Computer-aided software engineering (CASE), sometimes called computer aided systems engineering, is the automation of step-by-step methodologies for software and systems development to reduce repetitive work. CASE tools attempt to increase productivity and quality by facilitating the creation and revision of design specifications and program code. CASE tools provide automated facilities for producing charts and diagrams, screen and report generators, data dictionaries, analysis and checking tools, code generators, and document generators. The best CASE tools enforce common methods and standards, improve communication between users and technical specialists, organize and correlate design elements, automate tedious and error-prone portions of analysis and design, and automate code generation, testing, and control rollout. Which method of system development stresses intense?Also known as Agile methods. Stresses intense team-based effort. Breaks development into cycles, or iterations that add functionality. Each Cycle is designed, built, and tested in an ongoing process.
What is an early working version of an information system?The prototype is a working version of an information system or part of the system, but is meant to be only a preliminary model. Once operational, the prototype will be further refined until it conforms precisely to users' requirements.
When planning an information system a company must consider how a new system will interface with older systems which are called?CS235 System Analysis and Design. Is to create a physical model that will satisfy all documented requirements for the system?Midterm. |