Software Change and Prototyping

Coping with Change

• Change is usually necessary in software projects
• Change is important because business changes can lead to new and changed system requirements
• New technologies allow for system improvements and require application changes due to evolving hardware and platforms
• Change leads to rework, increasing costs due to implementing new functionality
• The cost of rework can be reduced by including extra activities to anticipate changes in software processes
• Change tolerance can be addressed using incremental models which will mean the first increment contain the main function with the additional increments accommodating for changes

Software Prototyping

• A prototype is an initial version of a system that demonstrates how the concepts will work.
• Prototypes are used to try out different design options.
• In requirements processes, prototypes help with requirements elicitation and validation activities
• Prototypes are used in the design process to develop a UI design
• Establish Prototype objective -> Define Prototype Functionality -> Develop Prototype -> Evaluate Prototype
• Prototyping examples URLs can be found here: https://www.framer.com/ and https://www.mockplus.com/

Software Prototyping Advantages

• Systems match user needs
• Improves system usability
• Reduces development effort

Software Prototyping Disadvantages

• It does not include error checking and recovery
• There is a focus on functional rather than non-functional requirements
• Prototypes are undocumented normally
• Prototypes probably will not meet quality standards

Incremental Delivery

• Rather than the system being delivered as a single thing, its broken down into increments which allows each part of the functionality to work
• User requirements are the main priority. and the requirements are included in early increments
• Once the development of an increment starts, the requirements are frozen until finished. However, later increments can continue to evolve
• Define Outline Requirements -> Assign Requirements to Increments -> Design System Architecture -> Develop System Increment (Back to Validate Increment if incomplete) -> System Complete -> Validate System -> Deploy Increment -> Final System

Incremental Delivery Advantages

• Main system functionality is developed first
• Early increments act as a prototype to help to elicit requirements
• Low risk of overall project failure

Incremental Delivery Disadvantages

• This is not suitable when the complete system specification is needed
• For most companies the system specification is part of the system development contract.
• Requirements are not defined in detail until an increment is to be implemented

Spiral Model

• The process is shown as a spiral rather than a sequence that can backtrack
• Each loop in the spiral represents a phase in the process
• There are no fixed phases like specification or design
• The loops in the spiral are chosen by required needs
• Risks are addressed and resolved through the process
• Objective Setting -> Risk Assessment and Reduction -> Development and Validation -> Planning

Spiral Model Advantages

• Well-suited for large scale projects
• Risk analysis helps to eliminate and avoid risk
• Evolving requirements are accommodated during the lifespan of the project
• Focuses on client approval

Spiral Model Disadvantages

• Smaller or low-risk projects are probably not a good fit
• Success depends greatly on the risk analysis
• High amounts of documentation because number of intermediate stages
• Can be expensive to implement due to large amount of loops

Rational Unified Process (RUP)

• Modern process model, derived from UML
• RUP includes aspects from three generic models
• RUP can adjust with requirement changing
• RUP is described from 3 perspectives: Dynamic, Static, and Proactive

RUP Phases

• Inception: External entries, and their interaction with the system
• Elaboration: Problems, Architecture, Project Plans, and Risks
• Construction: Design, Programming, Testing
• Transition: Moving a system to a user community, Training

RUP Static Perspective

• There are six main work flows
• Business Modelling. Use case modeling to represent business scenarios
• Requirements: actors are identified, and requirements are extracted from used cases
• Analysis and Design: 4 Models created (arch, component, object, sequence)
• Implementation: components are based on the models
• Testing: unit and integration testing
• Deployment: A release is created and installed for user environments

RUP Static Perspective Additional Workflows

• Also includes three additional workflows
• Configuration and Change Management to support changing requirements
• Project Management to manage the development
• Environment Tools providing appropriate software tools for the sw development team

RUP Proactive Perspective

• Develop Software Iteratively; Plan increments based on customer priorities and deliver highest priority increments first
• Manage Requirements: Explicitly document requirements
• Use Component-Based Architectures to organize the structure as reusable components
• Visualise Model Software with graphical UML software views
• Verify Software Quality ensures the organizational quality standards are met
• Control Changes to Software, implement a change management system