Agile software architecture aims to deliver value fast by evolving the architecture during the project based on what is important now, rather than defining it upfront. This reduces risk and waste by allowing decisions to be made based on actual knowledge gained during development. The architecture should be the simplest solution to support current functionality and evolve economically through changes without making the software worse. Principles like separation of concerns, refactoring, and tests that drive design help enable evolving the architecture in a controlled way.

1. Agile Software Architecture Cesario Ramos 04-2009

2. Code focussed Do what is important now Evolves during the project Defers Implementation Documentation focussed Do what is important in the long term Defined upfront Includes Implementation Agile Architecture Classic Architecture

3. Why agile software architecture?

4. Deliver Fast Increase ROI. Early validation of your business case. Give customers what they want when they want it.

5. Defer Commitment Reduce risk. Decide based on most possible knowledge. Keep yours and the customers options open.

6. Eliminate Waste Support something that does not add value now. Have the architecture slow you down

7. so we need sw architecture to... Be the simplest solution to support the current functionality. Change without increasing risk or waste. Change economically. Change without making the software worse. Evolve in early and refine later iterations.

8. Comparing with civil engineering

9. Based on concrete analysis using physics and mathematics. Based on things you know and change slowly. Plan, Do, Review. Plan the work, work the plan

10. Requirements Design Coding Testing Release Analysis Design Construction Inspection Release Software Development Civil Engineering Coding is NOT Construction

11. and then.... When do we test our requirements? When do we test our design? What if we overdo it? How do you handle changes? Requirements Architecture and Design Coding Testing Release

12. How to create agile software architecture?

13. High level guidelines. It’s helpful to know the functional modules needed to do the kind of business at hand. It’s helpful to know your current state and to know the desired future state modules architecture. (based in info known at the time.) You should include in the release plan the steps needed to go from current state to future state. Consider ROI in the decision making process Work on architectural modules only when actually needed. Evolve the architecture during the various releases Do not let quality decay, Refactor to the Open Closed. Validate, adapt and re-plan architecture.

14. Needed modules to do the business at hand?

15. DCI Architecture What the system IS Captures what is stable The domain classes What the system DOES User stories. Business objects.

16. Evolve the architecture?

17. Open Closed Principle A module should be open for extension and closed for modification

18. Refactoring as Fowler proposed Improving the design of existing code. Refactoring to be Open Closed. For handling future requirements. Refactoring Provides Value by Reducing Risk Reducing Waste

19. Separation Of Concerns Low Coupling Minimal dependencies Minimal side effects High Cohesion Single responsibility One reason to change

20. Tests Drive Design Supports you to look at your public API. Supports you to think about cohesion. Supports you to think about coupling. Supports you to not produce redundancies.

21. Readable code public void advanceTurn() { if ( characterHavingCurrentTurn + 1 < p layableCharacters .size()) characterHavingCurrentTurn ++; else characterHavingCurrentTurn = 0; }

22. Programming by Intention public void advanceTurn() { if (notAllCharactersInListHadTheirTurn()) nextCharacterInTheListGetsTheTurn(); else firstCharacterInTheListGetsTheTurn(); } private void firstCharacterInTheListGetsTheTurn() { characterHavingCurrentTurn = 0; } private void nextCharacterInTheListGetsTheTurn() { characterHavingCurrentTurn ++; } private boolean notAllCharactersInListHadTheirTurn() { return characterHavingCurrentTurn + 1 < playableCharacters .size(); }

23. Summary Agile Architecture helps you reduce risk and waste. OO/XP principles and practices make evolving architecture possible. Particular approach depends upon knowledge of domain, technology and project size.

24. Agile Software Architecture Cesario Ramos 04-2009