This text is about compositional programming, where programs are constructed by composing prewritten software building blocks. Three modern compositional paradigms are covered, listed in order of decreasing emphasis:A Software Product Line is a design for a family of programs. Each program is composed from predefined increments of program functionality. The Linux Kernel is the largest known product line whose family size exceeds 102000 distinct pro...

While standardization has empowered the software industry to substantially scale software development and to provide affordable software to a broad market, it often does not address smaller market segments, nor the needs and wishes of individual customers. Software product lines reconcile mass production and standardization with mass customization in software engineering. Ideally, based on a set of reusable parts, a software manufacturer can generate a software product based on the require...