Clafer: Lightweight Modeling of Structure, Behaviour, and Variability

TL;DR

Clafer is a compact modeling language that unifies structural, behavioral, and variability aspects of embedded software systems, enabling comprehensive system specifications within a single formalism.

Contribution

It introduces Clafer, a novel language combining rich structural and behavioral modeling with variability, built on first-order and linear temporal logic, unifying multiple modeling facets.

Findings

Successfully applied to a power window case study

Compared favorably against SysML, AADL, and other notations

Demonstrated expressive power and integration capabilities

Abstract

Embedded software is growing fast in size and complexity, leading to intimate mixture of complex architectures and complex control. Consequently, software specification requires modeling both structures and behaviour of systems. Unfortunately, existing languages do not integrate these aspects well, usually prioritizing one of them. It is common to develop a separate language for each of these facets. In this paper, we contribute Clafer: a small language that attempts to tackle this challenge. It combines rich structural modeling with state of the art behavioural formalisms. We are not aware of any other modeling language that seamlessly combines these facets common to system and software modeling. We show how Clafer, in a single unified syntax and semantics, allows capturing feature models (variability), component models, discrete control models (automata) and variability encompassing all these aspects. The language is built on top of first order logic with quantifiers over basic entities (for modeling structures) combined with linear temporal logic (for modeling behaviour). On top of this semantic foundation we build a simple but expressive syntax, enriched with carefully selected syntactic expansions that cover hierarchical modeling, associations, automata, scenarios, and Dwyer's property patterns. We evaluate Clafer using a power window case study, and comparing it against other notations that substantially overlap with its scope (SysML, AADL, Temporal OCL and Live Sequence Charts), discussing benefits and perils of using a single notation for the purpose.