Unified Operations for Variability in Space and Time.

Software and systems engineering is challenged by variability in space (concurrent variations at a single point in time) and time (sequential variations due to evolution). Managing both dimensions of variability independently is cumbersome and error-prone. A common foundation for operations on these dimensions is still missing, hampering the comparison and integration of existing techniques coping with variability in space and time as well as the design of new ones. In this paper, we address this problem by systematically identifying, categorizing, and unifying operations from contemporary tools and extending them to cope with both variability dimensions. Based on our gained insights, we identify gaps and trade-offs in current tools for managing variability in space and time, and discuss open challenges. The unified operations establish a common foundation that helps researchers and practitioners to gain a deeper understanding of existing techniques and tools for managing variability in space and/or time, analyze and compare them, and design new ones.