INFS 328 Systems Analysis and Design

Transcription

1 INFS 328 Systems Analysis and Design Session 5 Systems Analysis Lecturer: Prof. Ellis Edwin Badu, Dept. of Information Studies Contact Information: eebadu@ug.edu.gh College of Education School of Continuing and Distance Education 2017

2 Session Overview In session 4, you were introduced to planning for the development of an information system. After a systems analyst has decided to proceed with his systems project after the systems planning phase, he/she moves on to the systems analysis phase. In the system planning phase, preliminary request was done. In this phase, the process of gathering facts about the systems project, preparing documentation and creating modules that will be used to design and develop the system are considered. System analysis is the stage where an analyst attempts to study the old system of the organisation in order to understand the workings, inputs, outputs and other processes and services. This will help him/her to evaluate the old system in order to propose a more efficient system for the organisation. Slide 2

3 Session Outline The key topics to be covered in the session are as follows: Requirements Modelling Data and Process Modelling Development Strategies Other Analysis Techniques Requirements Discovery Method Joint Requirements Planning Preparation of System Requirements Document Slide 3

4 Topic One REQUIREMENT MODELLING Slide 4

5 Requirements Modelling Introduction There are three major activities of the analysis phase as can be seen in figure 1.1. These are requirements modelling, data and process modelling and development strategies. We shall look at these three and other ways of doing analysis. Upon completion of this topic, you should be able to recognise the principal activities of the systems analysis stage, and also the elements required to begin a formal analysis of an old information system. Slide 5

6 Requirements Modelling Requirements Modelling This involves fact finding to describe the information system you are working with. It also involves the identification of the requirements for a new system you are about to design. Such requirements include outputs, inputs, processes, performance and security. Outputs refer to electronic or printed information produced by the system. Inputs refer to necessary data that enter the system either manually or in an automated manner. Processes refer to the logical rules that are applied to transform the data into meaningful information. Slide 6

7 Requirements Modelling Requirements Modelling Performance refers to system characteristics such as speed, volume, capacity, availability and reliability. Security refers to hardware, software and procedural controls to safeguard and protect the system and its data from internal or external threats. Slide 7

8 Requirements Modelling Figure 1.1 Major activities of the Systems Analysis Slide 8

9 Questions Individual Assignment: Describe the major sections of the analysis phase of a systems project. Forum Question Slide 9

10 Topic Two DATA AND PROCESS MODELLING Slide 10

11 Data and Process Modelling Structured Analysis as a Data and Process Modelling Structured analysis identifies the data flow into a process, the business rules that transform the data, and the resulting output data follow. It is used to develop a logical model of the proposed (new) system and document systems requirements. This logical modelling show what the system must do regardless of how it will be implemented physically. Slide 11

12 Data and Process Modelling Structured Analysis as a Data and Process Modelling Later in the next phase (design phase), a physical model is built that describes how the system will be constructed an example of a structured analysis is a Data Flow Diagram see appendix. Other models that are also used to analyse the information systems are Process Descriptions and Object Oriented Analysis. Others include Information Engineering tools such as Entity Relationship diagrams and system flowcharts. These have been illustrated in the in the Appendix. Slide 12

13 Questions Individual Assignment: Name any three techniques used to analyse information systems. Forum Question Slide 13

14 Topic Three DEVELOPMENT STRATEGIES Slide 14

15 Development Strategies Strategies for the Analyses of Information Systems This is the third part of the analysis phase. Activities involved in this include; evaluation of alternative solutions, preparation of the systems requirements document, and presentation of the system s requirements document to management. The skills that are required to accomplish these are analytical skills and interpersonal skills. In addition, team oriented strategies have to be considered because information systems affect people throughout an organisation. The traditional model for developing systems had been an IT department using a structured analysis and gathering information about the current system by consulting users for inputs into the new system. Slide 15

16 Development Strategies Strategies for the Analyses of Information Systems With the Rapid Application Development (RAD) users are involved in every step of the systems development. While JAD focuses only on fact finding and requirements determination, RAD provides a fast-track approach to a full spectrum of system development tasks including planning, design, construction and implementation. Slide 16

17 Questions Individual Assignment: Describe the three activities involved in developing strategies Forum Question Slide 17

18 Topic Four OTHER ANALYSIS TECHNIQUES REQUIREMENTS DISCOVERY METHOD Slide 18

19 Requirement Discovery Method Introduction There are other techniques that are also used for analysis. For example, Requirements Discovery Methods, which consist of; fact finding techniques and Joint Requirements Planning (JRP) Slide 19

20 Requirement Discovery Method Requirements Discovery Requirements Discovery Methods are used to discover the problems and opportunities that exist in the current information system. They are also used to discover the requirements for the improved system. Fact finding technique is an example Slide 20

21 Requirement Discovery Method Requirements Discovery Fact Finding Technique Fact finding techniques also called Information Gathering. It is a classical set of techniques used to collect information about system problems, opportunities, solution requirements and priorities. It may include the sampling of existing documentation, reports, forms, files, databases and memos as well as research of relevant literature benchmarking other solutions and site visits to similar information systems. Others are observation of current information systems, surveys of management and information use community and interviews of appropriate managers, users and technical staff. Information gathered helps the analyst to understand the information system and gives the analyst an idea of what the system to be designed will be like. Slide 21

22 Questions Individual Assignment: Name other techniques used in analysing information systems Forum Question Discuss the fact finding technique and it s importance in the analysis stage of the systems development. Slide 22

23 Topic Five JOINT REQUIREMENTS PLANNING (JRP) Slide 23

24 Joint Requirements Planning Joint Requirements Planning The classic fact finding techniques described earlier, can be time consuming. An alternative way to accelerate requirements discovery and management is Joint Requirements Planning. These use facilitated workshops to bring together all the system owners, system users, system analysts, system builders and system designers to jointly perform system analysis. The analyst engages them in discussion, questions are asked and at the end of the workshop the analyst gets to understand what the information system is about. Slide 24

25 Questions Individual Assignment: What do you understand by Joint Requirements Planning? Forum Question Discuss the differences between the Requirement Discovery Method and Joint Requirement Planning Slide 25

26 Topic Six PREPARATION OF THE SYSTEMS REQUIREMENT DOCUMENT Slide 26

27 Preparing the Systems Requirement Document System Requirement Document This section is about documenting the requirements of a new system based on your understanding of the information system you analysed. A system requirement is a characteristic or feature that must be included in an information system to satisfy business requirements and be acceptable to users. A system requirement serves as a bench mark to measure overall acceptability of the finished system. Slide 27

28 Preparing the Systems Requirement Document Examples of System Requirements Output the website must report on-line volume statistics every four hours and hourly during peak periods. Inputs- the department head must enter over-time hours on a separate screen. Process the human resource system must interface properly with the existing payroll system. Performance system must support 25 users on line simultaneously. Controls the manager of the sales department must approve orders that exceed a customer s credit limit. Slide 28

29 Preparing the Systems Requirement Document System Requirements Document These requirements constitute the necessary specifications for the new system. System requirements specification therefore contains the requirements that will enable us to design our new system. It will describe the alternatives that were considered in a document, making specific recommendations to management. This document is also the starting point for measuring the performance, accuracy and completeness of the finished system before entering the next phase which is the design phase. The system requirements document is like a contract that identifies what the system developers must deliver to users. Slide 29

30 Questions Individual Assignment: Distinguish between the various forms of development strategies as outlined in analysis stage of systems development project. Forum Question Discuss some examples of systems requirement Slide 30

31 References Checkland, P. (1999). System Thinking, System Practice. Chiches: John Wiley. O Brien, J. A. (2003). Introduction to Information Systems: Essentials for E-Business Enterprise. Boston: Irwin. O Leary, I. and O leary, T. I. (2004). Computing Today. Boston: Mc Craw-Hill. Rowley, J. (1990). The Basics of Systems Analysis and Design for Information Managers. Ludin: Clive Bingley. Whitten, J. et al (2000). Systems Analysis and Design Methods. 6th ed., Boston: Mc Craw-Hill. Slide 31