Software Product Line Engineering (SPLE) aims at developing a large number of software systems that share a common and managed set of features . In the past years, it has been an active area in both research and industry. SPLE aims at improving productivity and reducing the time, effort, and cost required to develop a family of products (also called variants). The key point to achieve this goal is to manage the variability among various products of a Software Product Line (SPL). Variability is commonly expressed in terms of features, i.e., units of difference between software products. A product can thus be viewed as a set of features. Dependencies between features are typically represented in a Feature Model (FM) , whose ultimate purpose is to define which combinations of features (that is, which products) are valid . Behavior of both the features and the core behavior (i.e., the behavior shared by all products in the line) may be represented by (variants of) state machines [3, 13].