We model software for a variety of reasons: to assess the viability of or plan software systems to be built, to optimize use of (minimize, or ideally, avoid waste of) resources in response to inevitable changes in business, social, or technological environments, or simply to understand existing software systems. Indeed, as indicated by the model-driven approach to software development (Beydeda, Book, & Gruhn, 2005), models are becoming first-class members of organizations and software process environments that embrace them. The examples of collaboration in implementation of software are well-known (Nosek, 1998; Williams & Kessler, 2003). As models get large and complex, the need for creating them collaboratively in a systematic manner arises, and we propose pair modeling as an approach.