Application Engineering(product derivation), a key phase of the SPL process that can be tedious and error-prone, has been given far less attention compared to Domain Engineering. Implicitly, there arises the need for new product derivation techniques in the SPL research field. Therefore, this book proposes a methodology that covers both Domain Engineering and Application Engineering phases of the SPLE process and which focuses on the derivation of behavioural models of SPL products. By applying this methodology we want to produce behavioural models that belong to the analysis and early design levels of the software development life-cycle. Thus, the behavioural models obtained should describe the business and operational step-by-step workflows of activities/actions performed by the derived product. This methodology follows model driven engineering principles. This is due to the fact that in software engineering, models allow to express both problems and solutions at a hhigher abstraction level than code.