Scaling Agile Development via Architecture

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  1. For short projects (perhaps several weeks in length) you may do this work in the first few hours and for longer projects (perhaps on the order of twelve or more months) you may decide to invest a few days to do the initial architecture modeling.
  2. Think through the details just in time . As you can see in Figure 1, you will often choose to quot;model stormquot; focused issues on a JIT basis. These model storming sessions are typically impromptu events: one project team member will ask another to model with him, typically lasting for five to ten minutes (itis rare to model storm for more than thirty minutes).The people get together, gather around a shared modeling tool (e.g., a whiteboard), explore the issue until they're satisfied that they understand it, then they continue on (often coding). It is desirable to take a JIT approach to identifying the details because the requirements are going to change over time anyway, you can ask better questions based on your greater domain knowledge later in the lifecycle, and your stakeholders provide better answers because they've seen working software delivered on a regular basis. Frankly, there's no rush - if you have the ability to model something today you will have that same ability tomorrow.
  3. Allow good architectures to emerge over time . Although you can start with an architectural vision, or an architectural metaphor if you like, the fact is that the details will emerge as your system evolves to meet the changing needs of your stakeholders.
  4. Travel light . Don't create a 50-page document when a five-page one will do. Don't create a five-page document when a diagram will do. Don#39;t create a diagram when a metaphor will do. Remember Agile Modeling's They Ain't Gonna Read It (TAGRI) advice: close collaboration with others is a much more effective way to communicate your ideas than handing them documentation.
  5. Have a few overview diagrams . Just because you're traveling light doesn#39;t mean that there isn#39;t any documentation at all. I typically strive to create one or more navigation diagrams, diagrams that present an overview of the "landscape" of the system. Just like a road map overviews the organization of a town, your navigation diagram(s) overviews the organization of your system.
  6. Be flexible . The type of navigation diagram(s) that you create depends on the nature of the system that you are building. No one set of architectural views is right for every project. Instead, the nature of the project will help to define the types of views that you should consider creating.
  7. Display models publicly . Your architectural diagrams should be prominently displayed where your team can see them and, better yet, update them. For a co-located team your best approach is to simply have dedicated whiteboard space for the team. Distributed teams find that a Wiki with snapshots of diagrams and point-form text works well.
  8. 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."
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Figure 1. The AMDD lifecycle.

 Architecture Enables Scale
Although many software development projects are done by teams of less than ten people, some are much larger. Worse yet, your team may be spread out amongst multiple locations, time zones, and even organizations. To deal with the inherent complexities of managing such a team you will organize it into sub-teams, which in turn may be recursively organized into more sub-teams as required. These sub-teams will typically be responsible for developing one or more subsystems, and they must ensure that their work integrates easily

About the author

Scott W. Ambler's picture Scott W. Ambler

Scott W. Ambler is Principal at Scott W. Ambler + Associates. He is author of several books, including Disciplined Agile Delivery, Agile Modeling, Refactoring Databases: Evolutionary Database Design, and The Elements of UML 2.0 Style. Scott works with organizations worldwide to adopt agile software development techniques at scale.

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