Software Development Methodology

There are two renowned Software Development Methodology families, which are Waterfall and Agile, and they are quite abstract.

I called them abstract because they have many different implementations which are developed on top of them. Let's just think that Waterfall and Agile are ideas, and but the realisations vary based on specific industries or companies.

1) Waterfall

A picture worths thousands words. Let's start with the picture below.

Waterfall contains five phases as shown in the picture.

Only when the previous phase is completed can the next phase start, just like the water can only falls from the top to the bottom. Notably, the water cannot flow upward, which means that we cannot come back to the earlier phases once they are finished.

At each step, an artifact must be produced and delivered.

Other names: Linear model, Cascading model, Plan-driven development model.

We should know William Royce is the man who officially defined (not created) Waterfall model. However, he did not totally advocate this model. Royce said:

1. "I believe in this concept, but the implementation described above is risky and Invites failure", and
2. "Hopefully, the interaction between the various phases is confined to successive steps".

The believe that all requirements can be predicted and will follow all concrete plan are not feasible.

The aim of Agile Methodology is to enable an organisation to deliver and change quickly (very important in our digital era). These agile practices in software development may differ, they share some common features including iterative development, regular meeting with customers, deliver small and incremental changes.

"In February 2001 a group of 17 software gurus got together in Snowbird Utah to discuss the growing field of what used to be called Lightweight Methods and came up with what was called the Agile Manifesto and the term Agile Methods was coined The Manifesto States : We are uncovering better ways of developing software by doing it and helping others do it."

Through this work we have come to 4 key values:

1. Individuals and interactions over Processes and tools
2. Working software over Comprehensive documentation
3. Customer collaboration over Contract negotiation
4. Responding to change over Following a plan

That is, while there is value in the items on the RIGHT we value the items on the LEFT more

Another picture worths thousands words.

In Agile, there are typical 6 phases in one cycle: Plan - Design - Develop - Test - Release - Feedback. So basically, we are not developing or testing all features at a time. Instead, we do all 6 phases for one feature, then deliver it to the client to get the feedback, and then move to the next feature and so on. It is an incremental and iterative development.

One project may contain many cycles. One cycle may contain one or more features. It depends on the client.

Notably, the involvement of client is CRUCIAL in Agile. They act as the end-user, provide feedback, supervise the production, etc.

3) Scrum

Among many implementations in Agile family, Scrum is the most famous and frequent used (and frequently asked by the recruiters). This methodology allows self-organised teams to deliver highest value within the shortest time.

Scrum is made up of Role, Event, Artefact

3.1) Role

1. Product Owner: is a key stakeholder and represent the client. He provides the prioritized requirements and features to make up Project Backlog.
2. Scrum Master: is a facilitator who tracks the development process.
3. Team members: all members of the development team: Scrum Master, Developers, Testers, Analysts, etc.

3.2) Event

We should know Sprint is a short fixed-length cycle (1-4 weeks).

In one Sprint, there are 4 activities:

1. Sprint Planning Meeting: Product Owner defines what will be delivered in this sprint. Team members break it into smaller tasks and weight the workload.
2. Daily Meeting: is a Stand-up meeting. Everybody in the team usually meets at the early of the day to discuss "What I have done?", "What will I do?", "What are the obstacles?"
3. Sprint Review

• Team members demo what have been done in this sprint.
• Discuss what went well and the problem.
• Product Owner validates the deliverable.

4. Sprint Retrospective

• Team members identify the good and bad of this sprint.
• Find the main cause of the problem and improvement.

3.3) Artefact

1. Product Backlog: List of product features with priority assigned made by Product Owner.
2. Sprint Backlog: break the features in the Product Backlog and divide them into smaller tasks with estimated time for each task.
3. Sprint Goal: one statement about the achievement of this sprint.
4. Burn-down Chart: the remaining work and time. This is updated daily to provide visible progress.

4) Evaluation

Waterfall advantages:

• Suitable for Mission Critical Project, for example, Nuclear Factory, Space Craft Controller, Health, etc.
• Documentation is required for compliance. It is strict, carefully written, and seldom changed.
• The staged approach is logical and easy to follow.
• Emphasis on requirements and design before coding.
• Clear milestones which facilitate monitoring.
• Progress is documented and relevant artifacts produces.
• Roles and responsibilities are clearly defined.
• New team members can be easily incorporated into existing teams.

Agile advantages:

• Suitable for projects which are fast changing, unknown requirements at first.
• The deliverable does not need to be perfect in just one cycle.
• The system can be tested at anytime. As failure usually happens later, it is expensive to correct in just one phase.
• Customer feedback and involvement are available through the production period. They provide the necessary support, verify the system is built right, and validate the right system is built.