Unrealizability is a major challenge for GR(1), an expressive assume-guarantee fragment of LTL that enables efficient synthesis. Some works attempt to help engineers deal with unrealizability by generating counter-strategies or computing an unrealizable core. Other works propose to repair the unrealizable specification by suggesting repairs in the form of automatically generated assumptions.

In this work we present two novel symbolic algorithms for repairing unrealizable GR(1) specifications. The first algorithm infers new assumptions based on the recently introduced JVTS. The second algorithm infers new assumptions directly from the specification. Both algorithms are sound. The first is incomplete but can be used to suggest many different repairs. The second is complete but suggests a single repair. Both are symbolic and therefore efficient.

We implemented our work, validated its correctness, and evaluated it on benchmarks from the literature. The evaluation shows the strength of our algorithms, in their ability to suggest repairs and in their performance and scalability compared to previous solutions.