Ivy is a multi-modal verification tool for correct design and implementation of distributed protocols and algorithms, supporting modular specification, implementation and proof. Ivy supports proving safety and liveness properties of parameterized and infinite-state systems via three modes: deductive verification using an SMT solver, abstraction and model checking, and manual proofs using natural deduction. It supports light-weight formal methods via compositional specification-based testing and bounded model checking. Ivy can extract executable distributed programs by translation to efficient C++ code. It is designed to support decidable automated reasoning, to improve proof stability and to provide transparency in the case of proof failures. For this purpose, it presents concrete finite counterexamples, automatically audits proofs for decidability of verification conditions, and provides modular hiding of theories.

This paper surveys the work to date on Ivy, a language and a tool for the formal specification and verification of distributed systems. Ivy supports deductive verification using automated provers, model checking, automated testing, manual theorem proving and generation of executable code. In order to achieve greater verification productivity, a key design goal for Ivy is to allow the engineer to apply automated provers in the realm in which their performance is relatively predictable, stable and transparent. In particular Ivy focuses on the use of decidable fragments of first-order logic. We consider the rationale or Ivy’s design, the various capabilities of the tool, as well as case studies and applications.

Despite several decades of research, the problem of formal verification of infinite-state systems has resisted effective automation. We describe a system — Ivy — for interactively verifying safety of infinite-state systems. Ivy’s key principle is that whenever verification fails, Ivy graphically displays a concrete counterexample to induction. The user then interactively guides generalization from this counterexample. This process continues until an inductive invariant is found. Ivy searches for universally quantified invariants, and uses a restricted modeling language. This ensures that all verification conditions can be checked algorithmically. All user interactions are performed using graphical models, easing the user’s task. We describe our initial experience with verifying several distributed protocols.