Fitting the pieces together: a machine-checked model of safe composition

  • Authors:

  • Benjamin Delaware;William R. Cook;Don Batory

  • Affiliations:

  • University of Texas at Austin, Austin, TX, USA;University of Texas at Austin, Austin, TX, USA;University of Texas at Austin, Austin, TX, USA

  • Venue:
  • Proceedings of the the 7th joint meeting of the European software engineering conference and the ACM SIGSOFT symposium on The foundations of software engineering
  • Year:
  • 2009

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Abstract

Programs of a software product line can be synthesized by composing features which implement a unit of program functionality. In most product lines, only some combination of features are meaningful; feature models express the high-level domain constraints that govern feature compatibility. Product line developers also face the problem of safe composition - whether every product allowed by a feature model is type-safe when compiled and run. To study the problem of safe composition, we present Lightweight Feature Java (LFJ), an extension of Lightweight Java with support for features. We define a constraint-based type system for LFJ and prove its soundness using a full formalization of LFJ in Coq. In LFJ, soundness means that any composition of features that satisfies the typing constraints will generate a well-formed LJ program. If the constraints of a feature model imply these typing constraints then all programs allowed by the feature model are type-safe.