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• OBJECTIVEStudents will be able to explain the various stages of the system development life cycle (SDLC) and software engineering

Starting the System Starting the System Development ProcessDevelopment ProcessStarting the System Starting the System

Development ProcessDevelopment Process

The process of development can be costly, The process of development can be costly, the systems investigation stage may the systems investigation stage may require a preliminary study called a require a preliminary study called a feasibility study.feasibility study.

A feasibility studyA feasibility study is a preliminary study is a preliminary study where the information needs of prospective where the information needs of prospective users and the resource requirements, costs, users and the resource requirements, costs, benefits, and feasibility of a project are benefits, and feasibility of a project are determineddetermined

The goal of Feasibility Studies is to evaluate alternative system solutions and to propose the most feasible and desirable e-business application for development.

Four major categories Four major categories of feasibility studyof feasibility study

1. Organizational feasibilityHow well a proposes system supports the strategic e-business priorities of the organization.

2. Economic feasibilityIs concerned with whether expected cost savings, increased revenue, increase profits, reductions in required investment, and other types of benefits will exceed the costs of developing and operating the proposed system.

3. Technical feasibilityCan be demonstrated if reliable hardware and software capable meeting the needs a proposed system can be acquire or developed by the business in the required time.

4. Operational feasibilityIs the willingness and ability of the management, employees, customers, suppliers, and others to operate, use, and support a proposed system

System Development Life

Cycle (SDLC)

• To help create successful information systems, the System Development Life Cycle was developed. SDLC is an organized way to build an information system.

Phase 1 System Analysis

During this phase the development team focuses on completing three tasks:

1. Defining the problem and deciding whether to proceed

2. Analyzing the current system in depth and developing possible solutions to the problem

3. Selecting the best solution and defining its function

Analysts can document a problem or an entire system in several different ways.

1. Data Flow diagramsShows the flow of data through a system

(Allow students find diagrams online)

2. Structured EnglishUses English terms and phases to describe events, actions and alternative actions that can occur within the system

3. Decision TreeGraphically illustrates the event and actions that can occur in the system.

Phase 2 Systems Design

• During this phase the project team tackles the “how” of the selected solution.

• The different elements of the solution are designed in line with the requirements set out in the systems analysis. This will involve creating design specifications for hardware, software, databases, telecommunication/network links, personnel and procedures.

• Discuss diagram found on page 160 in AS&A Level ICT Through Diagrams Text Book.

Phase 3 Development

• During this phase programmers create or customize the software for the various parts of the system.

• They are two alternative paths:1. Acquisition2. Local Development

Acquisition

• The team may decide that some or all of the necessary system components are available as off-the-shelf hardware or software and may decide to acquire, rather than develop, these components.

• Advantages1. System will be built faster and cheaper2. Components are already tested proven

reliable although they may need to be customized to fit into the overall information system

Local Development• When an off-the-shelf solution is not

available or will not work with other parts of the system, the project team may need to develop a solution themselves.

• This means writing program code from scratch or making changes to existing software in the system.

• In many cases, project teams buy some components and develop others. Thus the follow both acquisition and local paths at the same time.

• During this phase, technical writers and/or online help authors work with the project team to produce the technical documentation and online help for the system.

• Testing is also an integral of Phases 3 & 4.

• After the software and equipment have been installed, the system should be tested.

• The typical approach to testing is to move from an individual component to (Unit testing) and then tests the components of the system with each other (system testing)

• Sample data is fed into the system. The processed information is then evaluated to see whether the results are correct. Errors are corrected, the necessary changes are made, and the tests are then run again.

• The next step is installation testing, when the system is installed in a test environment and tested with other applications used by the business.

• Finally, acceptance testing is done; the end users test the installed system to make sure that it meets their criteria.

Phase 4 Implementation

• In the systems implementation phase, the new information system is installed, and people are trained to use it.

• Another name for this phase is Conversion. It is the process of changing – converting-from the old system to the new and training people to use the new system.

• IS professionals must handle this process carefully to avoid losing or corrupting data or frustrating users trying to perform their work.

Types of Conversion

There are four approaches to conversion:

• Direct Conversion• Parallel Conversion• Pilot Conversion• Phased Conversion

1. Direct ConversionAll users stop using the old system at the same time and then begin using the new. This option is fast, but it can be disruptive and pressure on support personnel can be excessive.This approach is not recommended precisely because it is so risky. If anything is still wrong with the new system, the old system is not around to fall back on.

2. Parallel ConversionOld and new systems are operated side by side until the new one has proved to be reliable. However, keeping enough equipment and people active to manage two systems at the same time can be very expensive. Thus, the parallel approach is used only in cases in which the cost of failure or of interrupted operation is great.

3. Pilot Conversion• The new system is tried out in only

one part of the organisation. Once the system is working smoothly in that part, it is implemented throughout the rest of the organisation.

• This approach is certainly less expensive than the parallel approach. It also is somewhat riskier. However, the risks can be controlled because problems will be confined to only certain areas of the organisation. Difficulties will not affect the entire organisation.

Phased Conversion

• Users start using the new system, component by component by component. This option works only for systems that can be compartmentalized.

• This is an expensive proposition, because the implementation is done slowly. However, it is certainly one of the least risky approaches.

• Trainers and support personnel play a significant role during the conversion. Training courses usually involve classroom-style lectures, hand-on sessions with sample data, and computer-based training that users can work with on their own time.

Phase 5 Maintenance

• Systems maintenance first a systems audit and then an ongoing evaluation to see whether a system is performing productively.

• Maintenance has two main parts» A systems audit» Periodic evaluation

• In the systems audit, the system’s performance is compared to the original design specifications. This is to determine whether the new procedures are actually furthering productivity. If they are not, some redesign may b necessary.

• After the systems audit, the new information system is further modified, if necessary. All systems should be evaluated from time to time to determine whether they are meeting the goals and providing the service they are supposed to.