In finite-state verification, model checkers examine finite-state machines representing concurrent software systems looking for errors in design. Errors are defined as violations of requirements expressed as properties of the system. In the event that the finite-state machine fails to satisfy the property, a model checker is in some cases capable of producing a counterexample – an execution of the system demonstrating how the error occurs.
Property specifications are often written as Linear Temporal Logic (LTL) expressions. Once a requirement is expressed as an LTL formula, a model checker can automatically verify this property against the model.
Example
One example of such a system requirement: Between the time an elevator is called at a floor and the time it opens its doors at that floor, the elevator can arrive at that floor at most twice. The authors of "Patterns in Property Specification for Finite-State Verification" translate this requirement into the following LTL formula: