SYSTEM DEVELOPMENT METHODS

SYSTEM DEVELOPMENT METHODSBY SACHIN SREEKUMAR

SDLC

An information system is built with an objective and the activities performed to build the system are called System Development Life Cycle(SDLC).

SDLC consists of:1)Analysis 4)Implementation2)High-level design 5)Testing 3)Detailed Design 6)Deployment

BACKGROUND

Large scale system development projects were attempted by US military.

They developed a framework of a sequence of stages for developing a system. It is called as SDLC.

But the MIS oriented SDLC is different from others that it is more business oriented.

SYSTEM DEFINITION PHASE

System takes its shape and form logically.

A series of stages and steps are taken to develop a set of guidelines.

The key steps in the phase are:1)Preliminary analysis2)Feasibility study3)Information analysis4)System design

PRELIMINARY ANALYSIS

Normally conducted before an information system is designed.

Sometimes called preliminary investigation.

First step in the life cycle of a system.

Performed to understand requirements, objectives, scope and boundaries of the proposed system.

STEPS OF PRELIMINARY ANALYSISSteps taken under preliminary analysis are:

1)Assessment and survey of situation

2)Analysis of current system(if any)

3)Analyse system requirements and provide specifics

FEASIBILITY STUDY

Examines if a system can be developed successfully given the technical endowment, environment, resource constraints and organizational desirability.

We analyse whether the system can be developed and how to develop it.

dimensions are:1)Technical 2)Economic 3) Organizational

STEPS OF FEASIBILITY STUDY1)Define the objectives of feasibility study

2)Study the current environment

3)Analyse information requirements

4)Generation of alternative solutions

5)Report preparation

INFORMATION ANALYSISSystem is analysed from a logical perspective.System is defined in broader terms and is segregated in a hierarchy of black boxes.Each black box is a module with a specific role.The logical design is discussed with management and after suitable changes, physical design is developed.Data stores and processes are designed and integrated with the system.

INFORMATION ANALYSIS(cont..)

A complete logical view of the system which fulfils all requirements, is prepared in this stage.

Comprehensive project plan is prepared which includes activity-wise time schedule for system development, manpower requirements, budget, training requirements, testing plans, resource plans, installation plans, organizational plans, document plans.

SYSTEM DESIGNLogical design is detailed and a physical design document is prepared.

This document contains all implementation details of the system.

In this stage the entire system is put it on paper and explained in diagrammatic terms.

SYSTEM CONSTRUCTION PHASETwo step phase:

1)Application programme development

2)Procedures to interact with the system.

In the first step, design document is studied and an application programme developed.

This step requires maximum manpower and resources.

APPLICATION PROGRAMMINGSoftware that is the major part of the system is developed.Lines Of Code(LOC) are written in a computer programming language under a software environment to create software system.Construction Cost Model(COCOMO) is used to estimate project time and cost. Programming can be done using top-down or bottom-up approach.

STEPS IN APPLICATION PROGRAMMING

1)Designing the database and creating database structures

2)Designing and developing the user interface

3)Programming to create functions

4)Connecting the database to application

5)Incorporating the business logic into software

PROCEDURE DEVELOPEMENT

Users interaction with the system is laid down.

Different levels of users have different levels of access.

Procedures will clearly stated in the form of operating procedures and manuals.

Key tasks are described in flow charts.

IMPLEMENTATION PHASE

In this stage ,system is implemented at the organization after coding and testing.

Implementation tasks includes the following:1)Planning for implementation2)Communicating the implementation plan3)Organizing MIS personnel4)Selecting and procuring hardware

IMPLEMENTATION PHASE(cont..)

5)procuring the system software(OS)

6)Creating and deploying database

7)Training users

8)Creating and developing the physical infrastructure

9)Transiting to the new system

DEPLOYMENT

Once new system has been tested and ready, new system can be deployed using any of the 3 strategies:

1)Parallel strategy2)Direct customer strategy3)Phased approach

MAINTENANCE

Three types of maintenance:

1)Corrective (to fix any bugs that are discovered)

2)Perfective (to improve system performance)

3)Adaptive (to adapt new technology)

SOFTWARE DEVELOPMENT LIFE CYCLE(SWDLC)

Subset of SDLC.SWDLC deals only with the application software development life cycle of a system.Some popular software development methodologies are :1)Waterfall model2)Prototype model3)Rapid Application Development(RAD) model4)Spiral model

WATERFALL MODELClassic way of developing system.Systems are developed in phases and each phase is self contained.Overlaps are not allowed.Development work flows from one phase to another in a linear manner and progresses only when work on preceding phase is complete.

PHASES OF WATERFALL MODEL

1)Requirement analysis phase

Fact finding techniques(interview, questionnaire)

2)Design

3)Implementation

4)Testing

5)Deployment

6)Maintenance

WATERFALL MODEL

ADVANTAGES OF WATERFALL MODEL

Detailed early analysis cause huge advantages at later phases

If a bug found earlier, it is much cheaper (and more effective) to fix than bugs found in a later phase

Requirement should be set before design starts

Disciplined and well-structured approach

Effective for stable software projects

LIMITATIONS OF WATERFALL MODELUnderutilizes manpower(many team member stay idle).Real-life software development rarely follows this method.Changes are expensive.Need to finish every phase fully to start next phase.

PROTOTYPING MODELClient is anxious to complete the project.Developer has to create the software based on general set of objectives provided by the client.Model starts with requirement gathering.Developer and client meet to check if prototype of the proposed system works.The client reviews the software and suggests refinements, this results to an improved prototype.This process is repeated and with each iteration, prototype matures into a functional software.

PROTOTYPING MODEL(cont..)Prototyping process is not suitable for mission-critical projects.It may serve the organization well for small application.The problem is that clients may insist that the software be built based on early stages of the prototype.The developer, in an anxiety to complete, may use inappropriate components in the prototype, thereby affecting the long-term sustainability of the software.

SPIRAL MODELPioneered by bohem(1988), evolutionary in nature.Some features of both waterfall and prototyping is used.Software is created in incremental versions.In the early versions, software is not stable with iterations, software begins the take shape and form.Spiral starts with a plan, then prototype is prepared by some software development.Based on client feedback iterations will repeat.Spiral moves from one iteration to another, and after each iteration software improves.

SPIRAL MODEL

THANK YOU..