Agile software development techniques definitely scale. In Dr. Dobb's 2008 Agile Adoption Survey we saw that organizations are applying agile strategies in a variety of team sizes, including teams of over 200 people. For example, Lotus Sametime 7.5 was developed by an agile team of over 200 people at the peak of the project and within IBM there are other agile projects on the order of 500-600 people. At the Agile 2006 and 2007 conference, there were experience reports from agile teams of several hundred people. I expect the same at this year's conference, to be held August 4-8 (www.agile2008.org). Because one team organization structure does not fit all, this month I share strategies for organizing teams of various sizes.
A few years ago, Larry Constantine presented the best definition of a large project that I've ever run across: A large project is 20 percent bigger than any project you've successfully accomplished in the past. In other words, size is in the eye of the beholder, regardless of what the spammers may claim <smile>. For example, some organizations may consider a 20-person project to be huge whereas others may consider a 200-person project to be merely mid-size. For the sake of this discussion, the border between small and medium-sized project teams will be around 15, and between medium and large-sized teams around 50.
Agile in the Small
Most agile teams are less than 10 people and colocated. Although this sounds naive, Jim Highsmith has estimated that close to three quarters of all software development teams, be they agile or not, are less than 10 people in size. In this relatively simple situation, you can adopt a simple team organization structure, as in Figure 1. Agile team members, particularly on small teams, tend to be generalizing specialists (www.agilemodeling.com/essays/generalizingSpecialists.htm) who have one or more specialties such as Java programming or testing, at least a general knowledge of the software process and of the domain that they're working in, and the willingness to collaborate closely with and learn from others.
What you typically read about in the agile literature is how a team of developers, lead by a team coach or "Scrum Master", works closely with a product owner who represents the stakeholder community to build a high-quality working system on an incremental basis. What you don't hear about as often is what I call the "supporting cast"the technical experts, domain experts, and optional independent tester who help the team to succeed. Sometimes the team needs the help of technical experts, such as build masters to set up their build scripts or a database expert to help tune their database. Similarly, sometimes the product owner will bring in domain experts to work with the team, perhaps a tax expert to explain the nuances of a requirement or the sponsoring executive to explain the vision for the system. Effective agile teams often have an independent test team working in parallel that validates their work throughout the lifecycle (see "Scaling Test Driven Development, www.ddj.com/architect/205207998). Domain and technical experts are typically brought into the team for a short period of time, perhaps only a few hours or days, to help with a specific task. Independent testers and agile DBAs work with the team on an ongoing basis.