Separability principles for a general theory of software engineering: report on the GTSE 2015 workshop

The four GTSE (General Theory of Software Engineering) Workshops have brought awareness to, more or less mature, differing approaches, candidate theories for SE (Software Engineering). But one asks how to appraise the generality of these theories? And in case they are specialized sub-theories, are they amenable to combination into more general theories? The papers of the fourth GTSE Workshop addressed these questions by means of what can be collectively refer to as Separability Principles. In a sense, participants used well known techniques applied to design software systems to design SE theories. Separability is a powerful tool for understanding relations among SE candidate theories and guide how to assemble sub-theories into a general framework. Participants enthusiastically debated a series of related issues. The specialized vs. general theories questions were raised in diverse forms, such as, SE meaning multiple things, good predictive theories for narrow problems, ability of General theories to generate specific theories, and last but not least, whether "General" capture the contents of the workshop itself. The 4th GTSE edition was collocated with ICSE 2015 (International Conference of Software Engineering) in Firenze, Ital