Various modularization techniques are prominent candidates to cope with the complexity of software product lines (SPLs), such as aspect-oriented software development (AOSD), feature-oriented programming (FOP), and the like. The ACoM workshop aims to bring together researchers and industrial practitioners with different backgrounds to:

• understand the role and impact of contemporary modularization techniques on the design and implementation of SPLs;

• explore new, and potentially more effective, assessment methods to guide the application of modularization techniques in SPL development, and

• discuss the potential of using modularity assessment results to improve SPL development outcomes, to improve existing modularization techniques, and to foster the development of new techniques.

This is the fourth edition of the ACoM workshop, an itinerant event previously held at ICSE and OOPSLA.