Formeel

Formeel is a framework and language for formal methods used to specify and verify software systems. It provides a formal specification language, tooling for analysis, and a workflow for refinement from abstract models to concrete implementations.

The core language, Formeel Spec, supports algebraic data types, abstract state machines, and temporal properties. It integrates with model checkers and SMT solvers. The toolchain includes a parser, a type checker, a refinement engine, and back-ends that translate specifications into verification tasks. The design emphasizes modularity, enabling component-based specifications and compositional verification to manage complex systems.

Formeel originated from academic collaborations in Europe in the late 2010s and was released as an open-source project in 2020. It has continued to evolve through community contributions, with added libraries for concurrency, real-time constraints, and communication protocols. The project maintains documentation and example models to illustrate modeling patterns and verification workflows.

Applications of Formeel include safety-critical domains such as aviation, automotive, and medical devices, where formal specifications can accompany testing and validation. The framework aims to offer accessible introduction to formal methods while remaining compatible with established verification ecosystems. Within the formal-methods community, Formeel is recognized for its emphasis on refinement and modular reasoning, though it has not achieved widespread industrial deployment.