Week 11

System Development Life Cycle

Methods/Approaches/Models

Approaches to System Development

System Development Life Cycle

Methods/Approaches/Models

Waterfall Model

Prototype Model

Spiral Model

Extreme Programming

Unified Process

Agile Modeling

Rapid Application Development (RAD)

Joint Application Development (JAD)

Others methods..…

This is a conceptual model describing the phases involved in an information system development project.

•General steps of an SDLC methodology:

1. The existing system is evaluated.

2. The new system requirements are defined.

3. The proposed system is designed.

4. The new system is developed.

5. The system is put into use.

6. The new system should be evaluated once it is up and running.

It is the process of defining clear, discrete activities, and the work needed to complete each activity within a single project.

◦ Primary objectives: identify the scope of the new system

ensure that the project is feasible

develop a schedule, resource plan, and budget for the project

o Activities: define the problem

confirm project feasibility

produce the project schedule

staff the project

launch the project

Is the phase to better understand and document the business needs and the processing requirements of the new system. Toolkits for the job and technical methods consideration.

o Activities: gather information

define system requirements

prioritize requirements

generate and evaluate alternatives

review recommendations with management

This is where we design the logical solution system based on the requirements defined and decisions made during the analysis phase

o Activities: design and integrate the network

design the application architecture

design the user interfaces

design the system interfaces

design and integrate the database

prototype for design details

design and integrate the system controls

This is where the final system is built, tested, and installed to ensure that the users are all trained and that the organization is ready to benefit as expected from use of the system.

o Activities: construct software components

verify and test

convert data

train users and document the system

install the system

At this phase we keep the system running productively during the years following its initial installation by providing upgrades or enhancements patches for the software.

o Activities: maintain the system

enhance the system

support the users

Audit the system usage

Assess software performance

Describes a development method that is linear and sequential

Based on the metaphor that when one phase was finished, the development proceeds to the next phase and there is no going back

Does not accept the expected changes and revisions that become necessary with most projects

Some alternatives include joint application development (JAD), rapid application development (RAD), and spiral model

A systems development methodology in which a prototype is built, tested, and then reworked as necessary until an acceptable prototype is finally achieved from which the complete system or product can now be developed.

An iterative, trial-and-error process that takes place between developers and end users

Advantages: May provide the proof of concept necessary to

attract funding

Early visibility of the prototype gives users an idea of what the final system looks like

Encourages active participation among users and producer

Enables a higher output for user

Cost effective (Development costs reduced)

Increases system development speed

Assists to identify any problems with the efficacy of earlier design, requirements analysis and coding activities

Helps to refine the potential risks associated with the delivery of the system being developed

• Disadvantages: Possibility of causing systems to be left unfinished

Producer might produce a system inadequate for overall organization needs

User can get too involved where as the program can not be to a high standard

Structure of system can be damaged since many changes could be made

Not suitable for large applications

combines the features of the prototyping model and the waterfall model

shows the life cycle as a spiral, starting in the center and works its way around, over and over again, until the project is complete

intended for large, expensive, and complicated projects

General steps of Spiral Model:

1. The new system requirements are defined in details.

2. An initial design is created for the new system.

3. A first prototype of the new system is constructed from the initial design.

4. A second prototype is evolved by a fourfold procedure: (1) evaluating the first prototype in terms of its strengths, weaknesses, and risks; (2) defining the requirements of the second prototype; (3) planning and designing the second prototype; (4) constructing and testing the second prototype.

5. At the customer's option, the entire project can be aborted if the risk is deemed too great.

6. The existing prototype is evaluated in the same manner as was the previous prototype, and, if necessary, another prototype is developed from it according to the fourfold procedure outlined above.

7. The preceding steps are iterated until the customer is satisfied that the refined prototype represents the final product desired.

8. The final system is constructed based on the refined prototype.

9. The final system is completely evaluated and tested.

Advantages Estimates of the budget and schedule become

more realistic as work progresses because of the questions that have been raised Easier to cope with the changes inherent to

software development Software engineers can start working on the

project earlier rather than wading through a lengthy early design process

◦ Disadvantages A drawback of a spiral model is that estimates

of budget and time are harder to judge at the beginning of the project since the requirements evolve through the process.

NB: Summary: We have covered the three (3) basic SDLC models.

We recommend further reading on other

evolving models

Thank You