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Agile methods are a modern approach to incremental development.
They emphasze:
We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value:
- Individuals and interactions over processes and tools
- Working software over comprehensive documentation
- Customer collaboration over contract negotiation
- 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.
1) Our highest priority is to satisfy the customer through early and continuous delivery of valuable software.
2) Welcome changing requirements, even late in development. Agile processes harness change for the customer’s competitive advantage.
3) Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale.
4) Business people and developers must work together daily throughout the project.
5) Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done.
6) The most efficient and effective method of conveying information to and within a development team is face-to-face conversation.
7) Working software is the primary measure of progress.
8) Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely.
9) Continuous attention to technical excellence and good design enhances agility.
10) Simplicity – the art of maximizing the amount of work not done – is essential.
11) The best architectures, requirements, and designs emerge from self-organizing teams.
12) At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.
There are many variants of agile development, but they all share an emphasis on
source: The Agile Alliance
Many of these practices are familiar.
Extreme Programming and Scrum are specific forms of Agile
Key idea in all agile variations.
A user story is a mechanism for incremental requirements elicitation and analysis.
Stories are not Requirements
…despite the focus on functionality and non-functional characteristics.
Story Boards
When can you start using the house?
Teams typically try for 4-10 stories per iteration
Select stories to implement in current implementation
Often organized onto a task board
Velocity
Rate at which functionality (user stories) completed per iteration.
Most agile approaches define a fixed number of days per iteration
Add up the effort estimates of all stories completed during an iteration. This is the team’s current velocity.
Task Board
Contains stories to be completed in current iteration
Combines story cards and task notes
Task notes organized in columns
Setting a work pace that can be sustained indefinitely
Once a pace has been established, teams can measure velocity
(Kent Beck)
Each code unit
Test-Driven Development goes beyond our previously-cited “test first, code later” rule
The four steps above are repeated, adding new, tested functionality each time.
Design is on-going
Principles include
“You Ain’t Gonna Need It” - argument against early design of elaborate components for future use: “We going to need X eventually. We might was well design it now.” “YAGNI”
Design should be emergent
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