Towards Agile Architecture

Architecture provides the foundation from which systems are built and an architectural model defines the vision on which your architecture is based.

The scope of architecture can be that of a single application, of a family of applications, for an organization, or for an infrastructure such as the Internet that is shared by many organizations.Regardless of the scope, my experience is that you can take an agile approach to the modeling, development, and evolution of an architecture.

Here are a few ideas to get you thinking:

There is nothing special about architecture. Heresy you say! Absolutely not. Agile Modeling's value of humility states that everyone has equal value on a project, therefore anyone in the role of architect and their efforts are just as important but no more so than the efforts of everyone else. Yes, good architects have a specialized skillset appropriate to the task at hand and should have the experience to apply those skills effectively. The exact same thing can be said, however, of good developers, of good coaches, of good senior managers, and so on. Humility is an important success factor for your architecture efforts because it is what you need to avoid the development of an ivory tower architecture and to avoid the animosity of your teammates. The role of architect is valid for most projects, it just shouldn't be a role that is fulfilled by someone atop a pedestal.



You should beware ivory tower architectures. An ivory tower architecture is one that is often developed by an architect or architectural team in relative isolation to the day-to-day development activities of your project team(s).The mighty architectural guru(s) go off and develop one or more models describing the architecture that the minions on your team is to build to for the architect(s) know best. Ivory tower architectures are often beautiful things, usually well-documented with lots of fancy diagrams and wonderful vision statements proclaiming them to be your salvation.

In theory, which is typically what your architect(s) bases their work on, ivory tower architectures work perfectly. However, experience shows that ivory tower architectures suffer from significant problems. First, the "minion developers" are unlikely to accept the architecture because they had no say in its development.

Second, ivory tower architectures are often unproven, ivory tower architects rarely dirty their hands writing code, and as a result are a significant risk to your project until you know they actually work through the concrete feedback provided by a technical prototype. Third, ivory tower architectures will be incomplete if the architects did nothing else other than model because you can never think through everything your system needs.Fourth, ivory tower architectures promote overbuilding of software because they typically reflect every feature ever required by any system that your architect(s) were ever involved with and not just the features that your system actually needs.

Every system has an architecture. BUT, it may not necessarily have architectural models describing that architecture. For example, a small team taking the XP approach that is working together in the same room may not find any need to model their system architecture because everyone on the team knows it well enough that having a model doesn't provide sufficient value to them. Or, if an architectural model exists it will often be a few simple plain old whiteboard (POW) sketches potentially backed by a defined project metaphor.

This works because the communication aspects of XP, including pair programming and Collective Ownership, negate the need for architecture model(s) that need to be developed and maintained throughout the project. Other teams - teams not following XP, larger teams, teams where people are not co-located - will find that the greater communication challenges inherent in their environment requires them to go beyond word-of-mouth architecture. These teams will choose to create architectural models to provide guidance to developers as to how they should build their software. Fundamentally, the reason why you perform architectural modeling is to address the risk of members of your development team not working to a common vision.

Architecture scales agile. This is true of traditional techniques as well. Have a viable and accepted architecture strategy for a project is absolutely critical to your success, particularly in the complex situations which agile teams find themselves in at scale. Scaling issues include team size, regulatory compliance, distributed teams, technical complexity, and so on (see The Software Development Context Framework (SDCF) for details).

An effective approach to architecture enables you to address these scaling issues.