The following guest post, by Joy Beatty and Karl Wiegers, is a condensed preview of Chapter 21, “Enhancement and replacement projects,” from the upcoming book Software Requirements, Third Edition (which we’ll be publishing in August). A replacement project replaces an existing software system with a new custom-built system, a commercial off-the-shelf (COTS) system, or a hybrid of those. There are some challenges that most replacement projects share, including stuffing in unnecessary functionality, degrading the organization’s operational performance, users refusing to adopt the new system, and having such a large project that it never deploys. Focusing requirements practices on addressing these issues directly can increase the likelihood of a system replacement that delivers the desired more