Analyses of a software product line (SPL) model typically report variable results annotated with logical expressions to indicate the set of products for which each result holds. These expressions can be complicated and difficult to reason about when the SPL has lots of features and derivable products. In previous work, we introduced Neo4j Browser, a visualizer for graphical analysis results that highlights the results that apply to specific products. In this paper, we report on a controlled user study that evaluates the visualizer's effectiveness in helping the user (1) understand variable analysis results and (2) compare the analysis results of multiple products. Our findings suggest significant improvements in efficiency (30%), and correctness (22%), and significant reductions in cognitive load (42%).

Software Product Lines (SPLs) are families of related software products developed from a common set of artifacts. Most existing analysis tools can be applied to a single product at a time, but not to an entire SPL. Some tools have been redesigned/re-implemented to support the kind of variability exhibited in SPLs, but this usually takes a lot of effort, and is error-prone. Declarative analyses written in languages like Datalog have been collectively lifted to SPLs in prior work [1], which makes the process of applying an existing declarative analysis to a product line more straightforward. In this paper, we take an existing declarative analysis (behaviour alteration) and apply it to a set of automotive software product lines from General Motors. We discuss the design of the analysis pipeline used in this process, present its scalability results, and provide a means to visualize the analysis results for a subset of products filtered by feature expression. We also reflect on some of the lessons learned throughout this project.