Disciplined Agile Architecture: Initial Architecture Envisioning
An important aspect Disciplined Agile Delivery (DAD) is its explicit inclusion of an Inception phase where project initiation activities occur. Although phase tends to be a swear word within the agile community, the reality is that the vast majority of teams do some up front work at the beginning of a project. Some people will mistakenly refer to this effort this Sprint/Iteration 0 it is easy to observe that on average this effort takes longer than a single iteration (the 2009 Agile Project Initiation survey found the average agile team spends 3.9 weeks in Inception and the November 2010 Agile State of the Art survey found that agile teams have Construction iterations of a bit more than 2 weeks in length).
Regardless of terminology, agile teams are doing some up front work. Part of that initial work is identifying an initial technical architecture, typically via some initial architecture envisioning http://www.agilemodeling.com/essays/initialArchitectureModeling.htm. Because your architecture should be based on actual requirements, otherwise you’re “hacking in the large”, your team will also be doing some initial requirements envisioning http://www.agilemodeling.com/essays/initialRequirementsModeling.htm in parallel. Your architecture will be driven in part by functional requirements but more often the non-functional requirements, also called quality of service (QoS) or simply quality requirements. Some potential quality requirements are depicted in the figure below (this figure is taken from the Disciplined Agile Delivery book but was first published in Agile Architecture Strategies ).
Some architects mistakenly believe that you need to do detailed up front modeling to capture these quality requirements and then act upon them. This not only isn’t true it also proves to be quite risky in practice, see my discussion about Big Modeling Up Front (BMUF) for more details. Disciplined agilists instead will do just enough initial modeling up front and then address the details on a just-in-time (JIT) basis throughout construction. Of course it’s important to recognize that just enough will vary depending on the context of the situation, teams finding themselves at scale will need to do a bit more modeling than those who don’t. It’s also important to recognize that to address non-functional requirements throughout construction that you need to have more than just architectural modeling skills. This topic will be the focus of my next blog posting in this series.