ISDP1: system methodologies-SYSTEMS DESIGN UNIT 3

1.0 INTRODUCTION While in systems analysis the focus is on identifying the needs of the organization, the emphasis of systems design is to develop a new system that helps to achieve the goals and objectives of the organization and overcomes some of the shortcomings and limitations of the existing system. If the problems are minor, only small modifications are required. On the other hand, major changes may be suggested by systems analysis. In these cases, major investments in additional hardware, software, and additional personnel may be necessary. Regardless of the complexity and scope of the new system, it is the purpose of systems design to develop the best possible system. 2.0 OBJECTIVES By the end of this unit, you should be able to: • Explain the process of interactive design • Outline the various design techniques in systems • Outline the various design considerations • Describe procedures design • Discuss system design alternatives
  • Overview

For smaller design projects, systems design can be done in one stage. All of the steps and procedures described in this unit can be accomplished by the same design team over a given time span. For larger design projects, on the other hand, design is broken down into two phases. During the first phase, preliminary design, the overall system is investigated from a general point of view. During the second phase, detailed design, the steps of design are done in such a way that the new system can be acquired and implemented. This means that all reports and documents have to be specified in detail, that the inputs have to be specified and located, that the exact layout of all data on storage devices has to be developed, and so on.

It is unlikely that the entire system will be redesigned. In most cases, a number of applications will remain unchanged. Because of the high interaction between various applications, integrating the new system with the old system is essential. Making sure that the newly designed system is compatible with the existing applications and systems is called designing system interfaces. This is critically important to the success of the new system.

  • Interactive design

Today most computer systems allow the use of interactive process considerations. With this type of processing, people directly interact with the computer system through computer terminals. The computer and the user respond to each other in a real-time mode, which means within a matter of seconds or minutes. This type of processing brings new opportunities for good and effective design. The new design approach can include: (1) menu-driven system, (2) help commands, (3) table-lookup facilities, and (4) restart procedures.

Many new computer systems are menu driven. This is similar to a menu in a restaurant, which offers you the choice of one or more food items. With a computer system, a number of processing alternatives (a menu) are provided. These alternatives could be performing inventory control, accounts receivable, accounts payable, customer lookup, general ledger, and much more. You simply pick what you want to do, and then the computer provides you with another menu. Most people without extensive computer training can easily operate these types of systems. They simply respond to the questions the computer asks, and the computer does the rest.

Another commonly used design technique with interactive computer systems is the help command facility. Even with a menu-driven system, many people may have questions about exactly what they are doing or what response is desired from a particular question displayed on a terminal. Thus, many designers incorporate the help command into the computer program. Whenever a person is having difficulty in understanding what is happening or what type of response is expected, the command HELP or a similar command can be typed into the terminal. The computer will then respond with exactly which stage of processing the computer program is performing, what possible commands can be given by the person using the computer, and what is expected in terms of data entry.

The use of tables within an application is another very useful design technique. Most computer applications require a substantial amount of data entry. For example, a simple sales order might require a customer’s number, address, telephone number, and credit rating. Typically, however, the person entering the data does not have all of this information at his or her fingertips. To simplify things, elaborate tables can be developed and used by computer programs. A customer table, for example, might contain a customer’s number, name, address, telephone number, credit rating, the supplies and inventory ordered within the last year, the total naira amount of sales for the month, the total naira amount of sales for the year, and more. This table can also contain abbreviations for the customer’s number, name, and address.

Then it you want to enter data about this customer, you can simply type in one or more of these items. For example, if you are entering a sales order for a company, you simply type in its abbreviation, such as ABCO. The computer will then goes to the customer table and look up all the information required to make that sales order. This information is then displayed on a terminal screen for confirmation. The use of these tables can prevent wasting a tremendous amount of time entering the same data over and over into the system.

In the middle of an application, things can go wrong. There may be a temporary interruption of power, a line printer may run out of paper, a terminal may have a defective ribbon, and so on. When these problems occur, the application that is currently being run is typically shut down. With interactive processing, there needs to be a way to quickly restart the application where it left off. As a result, easy-to-use restart procedures are developed and incorporated into the design phase. With a restart procedure, it is very simple for an individual running an application to quickly restart it from where it left off. Restart procedures save both user time and computer resources.

For small companies or minor systems, design can be almost trivial. If you are considering the acquisition of a new piece of equipment, such as a terminal, there may be little design work involved. You already know exactly, what you want. It is simply a matter of going through the acquisition steps to get the best prices and features. On the other hand, if you are designing a completely new data processing system to handle such activities as payroll, accounts receivable, accounts payable, inventory control, distribution and warehousing, and numerous reports and documents for management, the design stage can be rather long and tedious. For these larger and longer projects, a systematic approach is needed. This approach should include general design considerations, evaluation and selection procedures, and development of written contracts when equipment and services are to be obtained from outside sources.

  • General design

A large design effort requires a number of general design considerations, including the following:

  • Organizational constraints.
  • Functional design.
  • Output design.
  • Input design.
  • Processing design.
  • File and data base design.
  • Procedures design.
  • Personnel and job design.

The first step in design is to lay out various restrictions and constraints placed upon you by the organization. Companies have limited time to develop new systems, limited financial resources, limited manpower,

limited equipment, and limited procedures. Being too conservative can also limit the overall effectiveness of the new system. You need to be as realistic and accurate as possible in specifying true organizational restrictions and constraints.

Functional design is a layout of the major functions of the organization. For example, a wood products company may perform two overall functions-one to manufacture paper products and the other to manufacture timber products. Each of these two major functions can be further subdivided into what the company produces. A functional chart can be developed to reveal the major functions and their sub functions. This functional chart is very similar (and in some cases almost identical) to the company’s organizational chart.

Once the functional chart has been developed, the desired information or output for each function and sub- function can be determined. When a large number of managers and decision makers is to be involved, small groups can be formed that analyze needs for their particular function. Each output from the computer for each functional area should be described with a great amount of detail and precision. The detailed layout of every report and output, the number of times the report is to be produced, how the report is to be distributed, and who should receive the various reports are described in detail. A short paragraph can be written describing each report, and in some cases, a layout chart or graphic picture can be used to reveal how each output should be constructed.

After managers have described in detail what they want from the new computerized system, it will be up to the data processing personnel to determine the best way to generate these reports and outputs. Managers should still be involved, however, in monitoring and controlling these activities, which include input, processing, file and data base design, and personnel selection and job design. Once data processing personnel know what managers want, they can work backwards to determine the input data needed to generate various reports and outputs. Layout charts can be used to describe the format of the input data. Next, processing design is done. This describes in detail how the input data is to be manipulated to produce the desired reports and documents. Processing design can be done with the use of such tools as flowcharts and decision tables. Once processing design is complete, file and data base design can be undertaken. File and data base design describes exactly how all the data is to be stored on the system.

Procedures design is another important and often overlooked area of designing a new computerized system. This involves developing rules,

regulations, and guidelines that are to be used while operating the new system. Computer security, crime and fraud prevention, and privacy policies are developed during procedures design as well.

Another key design consideration is personnel. For large and complex designs, new data processing personnel are usually needed to make the new system effective and operational. Personnel and job design, which is typically done by the data processing manager, describes what new people are required or how existing job titles and responsibilities are to be changed to accommodate the new computerized system.

Another important part of design is to determine which backup systems are required. In general, everything should have a backup, including all hardware, software, data, personnel, and supplies and facilities. What to do in case of a computer-related disaster should also be considered in the design phase.

The final design consideration is documentation. The documentation of the new system is very similar to the documentation of the existing system. Tools such as flowcharts, decision tables, grid charts, and so on can be employed.

  • Generating system design alternatives

When additional hardware and software are not required, alternative designs are generated by the members of the study team. The study team may also wish to get other personnel involved in generating alternative designs if the new system is more complex and involved than the existing system. If new hardware and software is to be acquired from an outside vendor, a formal request for proposals (REP) should be made.

There are a number of advantages to developing a formal RFP. To begin with, the RFP can make interacting with computer vendors easier. It can stipulate various ground rules. For example, most companies only have one or two people who interact with computer vendors directly. This prevents the computer vendors from trying to contact numerous managers and executives within the organization. Furthermore, one RFP can answer questions from many vendors, Without the RFP, the same questions could be asked dozens of times by different vendors. Even though developing the REP takes time, it can save time in the long run. Another advantage-is better price/performance ratios.

Vendors who know several companies will be bidding on the proposed new system often do a better-job estimating actual costs. As a result, the company may be able to obtain superior equipment for less money. The RFP can also prevent disputes and problems down the line. Typically, the RFP is included with the contract signed by the user and the vendor, protecting the company purchasing the equipment, software, and/or services.

The contents of the RFP should include some background information, the procedures that are to be followed during the selection process, a description of the existing company and data processing system, a description of the proposed system and its requirements, and a list of exactly what will be expected from the data processing vendor or manufacturer. The major part of the RFP is the description of the existing data processing system and the proposed system.

The request for proposals should be carefully written. The procedures to be followed are especially important. The computer vendors should be told which person on the study team is to be contacted, how their proposals will be evaluated, and the deadlines for proposals. In addition, the necessary support from the vendor, such as training, maintenance, installation restrictions, and so on, should be clearly stated.

  • System evaluation and selection

The final step in systems design is to evaluate the various systems design alternatives and to select that design which meets the needs of the new system at the least cost. Normally, a preliminary evaluation and a final evaluation are conducted before one design is selected.

When outside equipment, software, support, and maintenance are required, a contract between the organization and outside vendor is needed. Some computer manufacturers publish statistics on how fast their computer systems can perform certain operations, such as multiplying or dividing eight-digit numbers. These are called benchmark tests. Usually, computer manufacturers pick the data and the process to be done (i.e., multiplication) to make their system appear to be as fast as possible. As a result, it is very difficult to compare different computer systems using their tests and statistics. If you need to make speed comparisons, you can use the results of tests made by an independent group or organization. The best way to compare speed is to have the manufacturers perform a real application, such as payroll using actual payroll data. The same approach can be used if you are comparing storage capacity or any other system characteristics; actual data run on real applications is the best way to compare different computer systems.

Preliminary evaluation begins after the deadline for the submission of proposals. The purpose of this preliminary evaluation is to eliminate some of the proposals. Several vendors can usually be eliminated by investigating their proposals in detail. The remaining vendors are asked to make a formal presentation to the study team. Small demonstrations may also be conducted. Furthermore, the vendors should be asked to supply a list of organizations using their equipment for a similar purpose. These organizations are then contacted and asked to evaluate their hardware, software, and the vendor. It is also a good idea to ask these companies for further references that can be contacted. After evaluating the presentations, demonstrations, and the evaluations from other companies using similar equipment, the list of vendors is usually reduced to a few.

The final evaluation begins with a detailed investigation of the hardware, software, and support offered by each of the remaining vendors. The vendors should be asked to make a final presentation and to arrange for an extensive demonstration. The demonstration should be as close to real operating conditions as possible. Such applications as payroll, inventory control, and billing should be conducted with a large amount of test data. The same data and applications should be used by each vendor. Sometimes, it takes day or longer for each demonstration. But this is one of the best ways to learn more about the capabilities and limitations of a proposed data processing system.

After the final presentations and demonstrations, it is necessary to make the final evaluation and selection. During this stage, a detailed analysis of the hardware, software, and vendor is made. Cost comparisons, hardware performance, delivery dates, price, modularity, backup facilities, available software training, and maintenance factors are considered. Although it is good to compare computer speeds, storage capacities, and other similar characteristics, this is not enough. It is necessary to carefully analyze how the characteristics of the proposed systems will help the organization or company solve problems and obtain goals and objectives.

Although the exact procedure used to make the final evaluation and selection varies from one organization to the next, there are three commonly used approaches. These are: (1) group consensus, (2) cost-benefit analysis, and (3) point evaluation. In group consensus, a decision – making group is appointed and given the responsibility of making the final evaluation and selection. Usually, this group includes the members of the study team.


The objective of the design phase is to transform the detailed, defined requirements into complete, detailed specifications for the system to guide the work of the Development Phase. The decisions made in this phase address, in detail, how the system will meet the defined functional, physical, interface, and data requirements.

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