Approaches to System

Development System Development Life Cycle Approaches to System DevelopmentWaterfall Model Prototype Model Spiral Model Extreme Programming Unified Process Agile Modeling Rapid Application Development Joint Application Development

System Development Life Cycle

• conceptual model that describes the phases involved in an information system development project • possible to complete some activities in one phase in parallel with

some activities of another phase • phases are repeated as required until an acceptable system is found

• 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.

System Development Life Cycle

System Development Life Cycle

•Planning Phase•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 remainder of the

project

Activities:• define the problem• confirm project feasibility• produce the project schedule• staff the project• launch the project

System Development Life Cycle

•Analysis Phase•understand and document the business needs

and the processing requirements of the new system

Activities:• gather information• define system requirements• build prototypes for discovery of requirements• prioritize requirements• generate and evaluate alternatives• review recommendations with management

System Development Life Cycle

•Design Phase•design the solution system based on the requirements defined and decisions made during the analysis phase

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

System Development Life Cycle

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

Activities:• construct software components• verify and test• convert data• train users and document the system• install the system

System Development Life Cycle

•Maintenance Phase•keep the system running productively during the years following its initial installation

•upgrades or enhancements may be carried out to expand the system’s capabilities

Activities:•maintain the system•enhance the system• support the users

Approaches to System Development•Traditional Approach•also known as structured system development• Includes three techniques:• Structured analysis• Structured design

• Loosely coupled• Highly cohesive

• Structured programming• A sequence of program statements• A decision where one set of statements or another set of statements executes• A repetition of a set of statements

•Object Oriented Approach•views an information system as a collection of interacting

objects that work together to accomplish tasks • system consists of objects

Approaches to System Development

•includes three techniques:•Object-oriented analysis (OOA)• defines all of the types of objects • shows what user interactions are required

•Object-oriented design (OOD)• defines all of the additional types of objects necessary to

communicate with people and devices in the system • shows how the objects interact to complete the tasks • refines the definition of each type of object

•Object-oriented programming (OOP)•writing of statements using a programming language

Waterfall Model

•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

Waterfall Model

Prototype Model

•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

Prototype Model

Identify Problem

Convert to Operational System

Implement and Use Prototype

Develop Prototype

Revise and Enhance Prototype

If prototype inefficient

Problems

Next version

New requirements

Initial requirements

Working prototype

Prototype Model

• 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

Prototype ModelCost 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

Spiral Model

• 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

Spiral Model

Spiral Model

•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.

Spiral Model6. 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.

Spiral Model

•AdvantagesEstimates 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

• DisadvantagesA 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.

Extreme Programming

•discipline of system development that follows a specific structure that is designed to simplify and expedite the process of developing new software •developed by Kent Beck to be used with small

teams of developers who need to develop software quickly in an environment of rapidly-changing requirements •emphases on its use of two-person programming

teams and having a customer on-site during the development process

Extreme Programming•Relevant parts of XP that relate to design specifications:

1. How planning, analysis, design, and construction are all fused into a single phase of activity, and

2. Its unique way of capturing and presenting system requirements and design specifications.

• In XP, coding and testing are related parts of the same process, which means the programmers who write the code can also develop the tests.•The overall philosophy of XP is that code will be integrated

into the system it is being developed for and tested within a few hours after it has been written.

Extreme Programming

•Advantages of pair programming practice:More and better communication among developersHigher levels of productivityHigher-quality codeReinforcement of the other practices in XP, such as the

code-and-test discipline

•Disadvantages:Problems with unstable requirements No documented compromises of user conflictsLack of an overall design specification or document

Unified Process

•object-oriented system development methodology offered by Rational Software

•uses UML (a standard modeling notation for OO approach) for system models

•designed to reinforce six “best practices” for system development that are common to many system development methodologies • Develop iteratively• Define and manage system requirements• Use component architectures• Create visual models• Verify quality• Control changes

Unified Process

•Four Phases•Inception•Elaboration•Construction•Transition

•defines disciplines within each phase to make iterative development manageable

•defines roles played by developers and models created during the project

Agile Modeling

•popularized by Scott Ambler•practice-based methodology for modeling and documentation of software-based systems •proposed to be a collection of values, principles, and practices for modeling software that can be applied on software development project in a more flexible manner

Core practices:• Iterative and Incremental Modeling•Teamwork•Simplicity•Validation

Agile Modeling•Typical Agile modeling process would go like:• Listen for user stories from the customer.

•Draw a logical workflow model to gain an appreciation for the business decisions represented in the user story.

•Create new user stories based on the logical model.

•Develop some display prototypes. In doing so, show the customer what sort of interface they will have.

•Using feedback from the prototypes and the logical workflow diagrams, develop the system until you create a physical data model.

Rapid Application Development

•emphasizes speed of development through extensive user involvement in the rapid, iterative, and incremental construction of a series of functioning prototypes of a system that eventually evolves into the final system (or a version)

Rapid Application Development

Rapid Application Development•Consider using RAD when:•The team includes programmers and analysts who are

experienced with it

•There are pressing business reasons for speeding up a portion of an application development

•Working with a novel ecommerce application and the development team believes that the business can sufficiently benefit over their competitors from being an innovator if this application is among the first to appear on the Web

•Users are sophisticated and highly engaged with the organizational goals of the company

Rapid Application Development• Advantages:

It is useful for projects in which the user requirements are uncertain or imprecise.

It encourages active user and management participation, which increases end-user enthusiasm for the project.

Projects have higher visibility and support because of the extensive user involvement throughout the process.

Errors and omissions tend to be detected earlier in prototypes than in system models.

The iterative approach is a more “natural” process because change is an expected factor during development.

• Disadvantages:RAD prototypes can easily solve the wrong problems since problem analysis is

abbreviated or ignored.A RAD-based prototype may discourage analysts from considering other, more

useful technical alternatives.The emphasis on speed can adversely impact quality because of ill-advised

shortcuts through the methodology.

Joint Application Development

• involves the client or end users in the design and development of an application, through a succession of collaborative workshops called JAD sessions •developed in the late 1970s by Chuck Morris and Tony

Crawford • thought to lead to faster development times and greater

client satisfaction •a variation on JAD is the RAD which attempts to create an

application more quickly through strategies that include fewer formal methodologies and reusing software components •allows for the simultaneous gathering and consolidating of

large amounts of information • it opens up a lot of scope of inter-personal conflict