CP317 | Week 8 | Iterative Models

• CP317 Software Engineering focuses on iterative models.

Agenda

• Review of the waterfall model
• Introduction to iterative models
• Comparisons of iterative models with waterfall and incremental models
• Discussion of the prototype model and its comparison with the iterative model

Review of Week 8-1 Topics

• Software engineering process models
• Software development life cycle
• Predictive model vs. adaptive model
• Waterfall model and variations
• Waterfall with feedback model
• Sashimi model: waterfall with overlapping phases
• Incremental waterfall model
• V-model

Introduction - Disadvantages of the Waterfall Model

• It is inflexible
• No working software is produced until late in the life cycle
• High amounts of risk and uncertainty are involved
• Poor model for long and ongoing projects
• It cannot accommodate changing requirements
• Integration occurs at the very end, hindering early identification of bottlenecks or challenges

Iterative Model

• It involves initial, simplified software implementation
• It progressively gains complexity and a broader feature set until complete
• It includes initialization, planning, requirements, design, implementation, verification, evaluation, and deployment stages.

Iterative Model Example

• An online banking system can be developed using this model
• Data communication and authentication with login and information views is included
• It includes online money transfer and online investments

Advantages of the Iterative Model

• It generates working software quickly and early
• It is more flexible and less costly to accommodate requirement changes
• Testing and debugging are easier because of smaller iterations
• Risks are easier to manage due to the identification and handling of risky pieces during iteration
• Each iteration is an easily-managed milestone

Disadvantages of the Iterative Model

• Each phase of an iteration is rigid
• Problems may arise pertaining to system architecture because not all requirements are gathered up front for the entire software life cycle

Iterative Model vs. Waterfall Model

• Waterfall models use subjective measurement of progress while iterative models use objective measurement.
• Waterfall models involve delayed integration and testing
• Iterative models have continuous integration and testing
• Waterfall models deliver nothing until the end, whereas iterative models produce something runnable every iteration
• Waterfall models face difficulties at the end of the project, iterative models face difficulties at the start of the project
• Subjectivity is based on personal opinion, assumptions, and interpretations
• Objectivity is based upon observation of measurable facts

Iterative Model vs. Incremental Model

• The Iterative model initially features all features with low fidelity
• Incremental model initially offers fewer features with full fidelity
• Incremental model follows linear paths of progression with a fixed number of steps, ending at completion
• Iterative is completed in cycles or loops

Increment vs Iteration

• Increment: makes something bigger through accretion
• Iteration: makes something better through repetition
• Increment is an increase or addition, especially one of a series
• Iteration is the process of doing something again and again, usually to improve it
• Scrum is incremental, Lean is iterative

Prototype Model

• A prototype is a rudimentary software product, not complete, but representative of the final product
• This is a process where a prototype is designed, built, and features are added to achieve an acceptable product.
• Prototypes demonstrate the features of a system

Advantages of Prototypes

• Improved Requirements
• Encourages Active User Participation
• Common Vision
• Helps Resolve Discrepancies between the client and the company
• Gives Users a Feel for the Final System
• Helps Determine Technical Feasibility
• Helps Sell the Idea of a Proposed System

Disadvantages of Prototypes

• Narrowing Vision
• Schedule Pressure
• Leads People to Believe the Final System Will Follow
• Gives No Indication of Performance under Operational Conditions
• Leads the Project Team to forgo Proper Testing and Documentation

Prototype Model vs. Iterative Model

• Prototype model involves Requirement Analysis, Design, Building and Prototyping, Refining Prototype, and Evaluation by customer
• Iterative model involves Initialization, Planning, Requirements, Design, Implementation, Verification, Evaluation, and Deployment

Similarities of Prototype and Iterative Models

• Both models initially provide all possible features with low fidelity
• Both models employ iterative processes

Differences of Prototype and Iterative Models

• The prototype model requires direct customer involvement

Summary

• An overview of concepts, advantages and disadvantages of iterative models
• Comparisons between the iterative model and the waterfall model
• Comparisons between the iterative model and the incremental model
• An overview of the prototype model and comparisons between the prototype model and the iterative model

Announcement

• Test 2 is scheduled for the next Monday (March 10) and will cover topics for weeks 5-8
• Bring a laptop to the test, which will be in LH3094.
• Stay after the test for drawing lots
• Group project software design document is due March 21.