Spectra: a specification language for reactive systems

Abstract

We introduce Spectra, a new specification language for reactive systems, specifically tailored for the context of reactive synthesis. The meaning of Spectra is defined by a translation to a kernel language. Spectra comes with the Spectra Tools, a set of analyses, including a synthesizer to obtain a correct-by-construction implementation, several means for executing the resulting controller, and additional analyses aimed at helping engineers write higher-quality specifications. We present the language in detail and give an overview of its tool set. Together with the language and its tool set, we present four collections of many, non-trivial, large specifications, written by undergraduate computer science students for the development of autonomous Lego robots and additional example reactive systems. The collected specifications can serve as benchmarks for future studies on reactive synthesis. We present the specifications, with observations and lessons learned about the potential use of reactive synthesis by software engineers.

Unrealizable Cores for Reactive Systems Specifications

“…We have implemented our ideas on top of Spectra [20], [28], with the performance heuristics from [13]. Our implementation includes QuickCore and Punch.…”

“…1), taken from [23], which has appeared in several variants in previous GR(1)-related papers [2], [7], [8], [25]. The specification is written in Spectra format [20], [28]. It is small and simple, to fit the paper presentation.…”

“…Reducing Higher-Level Constructs into Pure GR (1) Recall that many higher-level language constructs can be reduced to pure GR(1) form by replacing them with additional auxiliary variables as well as new guarantees or assumptions. See, e.g., [19], [20].…”

“…Finally, our third contribution is the extension of core computations to correctly handle specifications that include, beyond pure GR(1) elements, higher-level constructs such as patterns, past LTL operators, monitors, and counters, as supported, e.g., in Spectra [20]. This is important in order to correctly apply core computations to these more compact and readable specifications, and to present the results not at the level of the internal representation but at the abstraction level used by the engineer who wrote the specification.…”

“…We implemented our ideas on top of Spectra, a rich specification language and open source tool set for reactive synthesis [20]. All our algorithms are implemented on top of, and compared to, recently suggested heuristics for realizability and core computations for GR(1) [13].…”