Christian Federspiel worked for Siemens VAI in the field of industrial automation from 1990 to 2006. He did worked on R&D and commissioning of large software applications. He led an Agile software development team for five years. He is now with Cataylsts and does consulting and project work in various areas of software development (e.g., requirements engineering, use cases, Agile software development, test-driven development, Agile modeling/domain-driven design, and software architecture). He holds a master's degree in computer science and is a member of the Agile Alliance. He can be reached at federspiel at catalysts.cc.