From Single- to Multi-Variant Model Transformations: Trace-Based Propagation of Variability Annotations

In annotative approaches to model-driven product line engineering (MDPLE), model elements are decorated with variability annotations defining the product variants in which they are included. A multi-variant model transformation (MVMT) has to propagate these annotations from source to target models. We propose trace-based propagation as a grey box solution to this problem: After executing a variability ignorant single-variant transformation (SVMT), annotations are propagated a posteriori based on the trace produced by the SVMT. Trace-based propagation allows to reuse SVMTs, and can be implemented in a generic way, independently of SVMT languages and tools, making it suitable for use in a heterogeneous MDPLE environment. A formal proof demonstrates that trace-based propagation achieves commutativity of filters and transformations, obviating the need to manually edit target model annotations.