Book excerpt: Typically, telecommunications services are implemented in software. Feature interaction is the term used to describe interference between services or features; most attention is given to cases where the interference is undesirable, ie. there is an incompatibility. In telecommunications, control and data is distributed and on such a large scale that software development is by numerous disjoint teams; by its nature, therefore, this software experienced the feature interaction problem first. But, while the workshop focuses on communications services, the subject has relevance to any domain where separate software entities control a shared resource.