Architecture a Key Factor in Scaling Agile

Scott Ambler's article "Scaling Agile Development Via Architecture" in the November issue of Agile Journal summarizes strategies for Agile teams regarding architecture, and argues that an effective approach to architecture is an important aspect of scaling agile software development.

Many of the architectural strategies proposed by Ambler describe trade-offs; the implication is that you must tailor an approach which meets your unique situation.

Agile Architecture Strategies

1. Focus on collaboration over documentation. "Agile architects" are ... not simply people who document their vision and hand it off to developers.
2. Prove it with code. Everything looks good on a whiteboard, or in a modeling tool.
3. Keep it simple. Agile software developers model ... in ways which are very different than traditionalists.
4. Use the simplest tools. ... free form diagrams, ... simple sketches ...
5. Think through the big issues up front.
6. Think through the details just in time. ... "model storm" focused issues on a JIT basis.
7. Allow good architectures to emerge over time. ... the fact is that the details will emerge as your system evolves to meet the changing needs of your stakeholders.
8. Travel light. Remember Agile Modeling's They Ain't Gonna Read It (TAGRI) advice.
9. Have a few overview diagrams. Just like a road map overviews the organization of a town, your navigation diagram(s) overviews the organization of your system.
10. Be flexible. ... the nature of the project will help to define the types of views that you should consider creating.
11. Display models publicly. Distributed teams find that a Wiki with snapshots of diagrams and point-form text works well.  
12. Take a requirements-driven approach. Your architecture must be based on actual requirements put forth by your stakeholders, otherwise you are "hacking in the large."
13. Model with others. By working collaboratively you will create a higher quality product, will develop a shared vision, and will learn from one another.

Ambler's approach is rather distinctive from the traditional "big design up front" style in its view of the architect role:

To avoid an ivory tower architecture, the members of the core architecture team take active roles ... working with them to prove portions of the architecture via concrete experiments. From the point of view of the development sub-teams, the architect acts as both an architectural consultant and as an active member of the sub-team. In other words, the architect is another member of the team who gets his hands dirty coding.

The article includes an introductory diagram outlining the Agile Model Driven Development project lifecycle.

In conclusion, Ambler discusses how Architecture Enables Scale, addressing large teams, distributed / non-colocated teams, and projects delivering components to huge projects spanning 10 years or more. Using these strategies, he proposes that the core architecture team and the models which they create will help to promote a shared, evolving vision throughout the lifetime of even the most complicated project.

Scott Ambler is Practice Leader Agile Development, IBM Methods Group, and the originator of both Agile Model Driven Development and Agile Data Modeling.  The tagline on his homepage reads: A good developer knows that there is more to development than programming...