Spiral Model in Software Development

Risk Solution: Building a Prototype of the Data Access Subsystem

• The spiral model is a meta-model that subsumes all other models.
• The spiral model uses a prototyping approach to first draft the solution before embarking on the actual product.
• Iterations along the spiral model can be considered as the evolutionary levels through which the complete system is built.

Agile Methodology

• Agile methodology was first discussed in 2000 in Oregon, USA, with the goal of speeding up development times to bring new software to market faster.
• Three key ideas of Agile are:
  • Speed to market
  • Rapid feedback
  • Continuous improvement
• In 2001, the Manifesto for Agile Software Development was created with 12 principles.

Agile Approach: Iterative and Incremental

• A large project is divided into small increments called sprints.
• Development is carried out by small teams of 4 to 9 people.
• The schedule is divided into fixed time boxes, typically 2 to 4 weeks.
• Each sprint is a time box during which the team completes part of a software project.
• Each sprint ends with fully tested code, ready to put into production.

Agile Development - Sprint

• After each sprint, the code may be:
  • Released (original agile method)
  • Combined with code from other sprints for subsequent release
  • Incorporated into a larger code base (spiral development)

Scrum

• Scrum is the most widely used agile method for software development.
• Scrum roles include:
  • Scrum Master
  • Product Owner
  • Development Team

Scrum Roles

• Scrum Master:
  • Understands the theory, practices, rules, and values of Scrum
  • Helps others improve interactions to maximize the value by the Scrum team
• Product Owner:
  • The bridge between the business part and the technical part of the project
  • Responsible for writing user stories and keeping the Product Backlog up to date
• Development Team:
  • Transforms expressed needs into usable functionalities
  • Includes developers, software architects, functional analysts, graphic designers, etc.

Product Backlog

• Contains all the user stories that will be turned into tasks for the Scrum team to select and plan in upcoming sprints.
• Product Owner is in charge of managing and keeping the Product Backlog up to date.

Sprint Backlog

• Contains all the tasks that need to be completed during a sprint.

Epics - User Stories - Tasks

• Epic:
  • A functionality of the product to be developed
  • A multiple sets of user stories grouped by categories or themes
• User Story:
  • A statement of a user expectation
  • Not a task, nor a specification
• Task:
  • Technical activities that help respond to user stories
  • Tasks should be same-sized but may be of different nature: design, development, test, etc.

Scrum Meetings

• Three types of meetings:
  • Sprint Planning Meeting
  • Daily Scrum Meeting
  • Sprint Retrospective Meeting

Sprint Planning Meeting

• Goal: The development team selects the priority elements of the Product Backlog to complete in the current sprint.

Daily Scrum Meeting

• Daily synchronizing meeting
• Goal: to enable team members to gather on a daily basis to discuss tasks and work progress as well as potential problems to overcome possible blockages and promote mutual support.

Sprint Retrospective Meeting

• Toward continuous improvement
• Takes place at the end of the sprint
• Goal: discussing and taking a step back from the latest sprint to optimize interactions between individuals, raise product quality, and improve productivity.
• Tools:
  • Burnup chart
  • Burndown chart
  • Velocity

Mixed Processes

• Many large projects use processes that mix aspects of the four types of software process.
• Examples:
  • A project with well-understood requirements might use a modified waterfall approach to specify the requirements and system design, followed by a series of agile sprints.
  • A project with vague requirements might use iterative refinement to clarify the requirements, followed by a modified waterfall model to build the final version.
  • With spiral development, new components may be developed as a series of sprints.

Waterfall Model

• A pure sequential model is not possible, and some form of iteration is necessary.
• Examples of limitations include:
  • Feasibility studies may reveal gaps in requirements specification.
  • Client changes or development team decisions may impact technology choices.

Modified Waterfall Model

• This model works best when:
  • Requirements are well understood.
  • Design is straightforward.
• Examples of suitable applications include:
  • Converting manual data processing systems with clear requirements.
  • Developing new versions of systems with closely derived functionality.
  • Building portions of large systems with clearly defined requirements.

Spiral Model

• The spiral model subsumes other models, including the waterfall model.
• Key features include:
  • Prototyping approach to draft solutions before actual product development.
  • Iterations along the spiral model represent evolutionary levels of system building.
  • Results of each spiral are incorporated into the larger base system.

Agile Methodology

• Originated in 2000 in Oregon, US, as a response to the need for faster development times.
• Focuses on iterative and incremental development.

Spiral Development

• An iterative and incremental model with emphasis on risk analysis.
• 4 main phases:
  • Planning
  • Design
  • Construct
  • Evaluation
• Each iteration is equivalent to a spiral.

Spiral Development Schema

• 1st quadrant: Requirements gathering and analysis at the start of each spiral.
• 2nd quadrant: Solution evaluation, risk identification, and strategy development.