Presentation on theme: "Info1409 De Montfort University Lecture 3 The Systems Development Life Cycle Systems Analysis & Design Academic Year 2008/9."— Presentation transcript:
info1409 De Montfort University Lecture 3 The Systems Development Life Cycle Systems Analysis & Design Academic Year 2008/9
info1409 De Montfort University Objectives By the end of this lecture you will Have been introduced to the Systems Development Life Cycle. Learned about the stages (or steps) involved in system analysis. Been introduced to the ‘waterfall model’ and possible alternatives
info1409 De Montfort University Recap from Lecture 2 In Lecture 2 we made the following observation: Systems Analysis and Design is a step by step process for developing high quality information systems
info1409 De Montfort University Structured Analysis Structured analysis is the traditional way of moving from old outdated, or inefficient systems to new and improved ones. This tradition uses a concept called the Systems Development Life Cycle.
info1409 De Montfort University Systems request Planning a new system usually begins with a formal request called a ‘system request’ The request describes problems, or desired changes in an information system or business process
info1409 De Montfort University Systems Planning phase The systems request usually initiates the Systems Planning phase of the System Development Life Cycle. It can come from a top manager, a planning team, a department head, or even the IT Department of an Organisation.
info1409 De Montfort University Systems Planning Systems planning is the first stage in the System Development Life Cycle In this first stage a preliminary investigation will take place to identify the nature and scope of the problem (or business opportunity)
info1409 De Montfort University The entire Systems Development Life Cycle.(SDLC) Describes activities and functions that all systems developers perform, and consists of the following steps (or stages): 1. System Planning (including Feasibility) 2. System Analysis 3. System Design 4. Systems Implementation 5. Systems Operation, support and security
info1409 De Montfort University SDLC Models The systems Development Life cycle can be described or modelled in different ways. The most usual and well known model is called the ‘Traditional Life Cycle or (Waterfall) model’ The following is an illustration of what is meant by the ‘Waterfall model’
info1409 De Montfort University
The Waterfall model explained When each phase is completed it produces what is called a deliverable or end product This deliverable then flows to the next phase In the following slide (fig 1-27)the adjacent phases interact and are indicated as dotted lines.
info1409 De Montfort University Page 21 Shelley et al
info1409 De Montfort University Activity time Instructions: Work with the student sitting next to you. If you do not have one, then try to get involved with a student or students either behind you, or in front of you. Take ONE stage each of the SDLC Discuss and record what you think the activities in that stage would be.
info1409 De Montfort University Feedback This is the time when you will get an opportunity to ask any questions, and discuss what you have decided. Time will be up in 5 mins!!!!
info1409 De Montfort University Stage 1 –Systems Planning After the systems request the preliminary investigation begins A key part of this investigation is a Feasibility Study The Feasibility study reviews the anticipated costs and benefits to the Organisation and recommends a course of action.
info1409 De Montfort University Stage 2 – Analysis The results of the preliminary investigation and feasibility study lead to the second stage of the SDLC. The purpose of the Systems Analysis phase is to build a logical model of the new system The first step is requirements modelling.
info1409 De Montfort University Analysis continued.. Requirements modelling In requirements modelling, the analyst investigates the business processes to document what the new system must do. Requirements modelling continues the investigation that began in systems planning.
info1409 De Montfort University Stage 3 - Systems Design. At this stage you design the User Interface 1. Identify all necessary inputs, outputs and processes. 2. Design internal and external controls 3. Show programmers how to transform the logical design into program modules and code. (application architecture)
info1409 De Montfort University Design (continued) The result of the Design stage is documented in the System Design Specification This is presented to Managers and users for review and approval.
info1409 De Montfort University Stage 4 -System Implementation …involves the following activities: Programs are written, tested and documented. The system is installed. Final preparations are made to convert data to the new system’s files, and to train users). A system evaluation is conducted
info1409 De Montfort University Stage 5 – Systems Operation, Support and security During this stage, the IT staff maintain, enhance and protect the system. Maintenance corrects errors, and adapts to changes in the environment such as new tax rates. Enhancement gives new features and benefits. Security controls safeguard the system
info1409 De Montfort University Well Designed Systems “A well designed system will be secure, reliable, maintainable and scalable. A scalable development can expand to meet new business requirements and volumes. Information systems development is always a work in progress” Page 22 chapter 1 Shelley et al Systems Analysis & Design 6 th Ed.
info1409 De Montfort University Alternative SDLC model This alternative model focuses on the interaction of planning, analysis and design tasks which leads to implementation followed by operation and support.
info1409 De Montfort University Recommended Reading Chapter 1 up to pages of the recommended text ‘Systems Analysis & Design’, Shelley Cashman Series, Thomson Course Technology (2006)