  We introduce two new major features of the open-source model checker Kind 2
which provide traceability information between specification and design
elements such as assumptions, guarantees, or other behavioral constraints in
synchronous reactive system models. This new version of Kind 2 can identify
minimal sets of design elements, known as Minimal Inductive Validity Cores,
which are sufficient to prove a given set of safety properties, and also
determine the set of MUST elements, design elements that are necessary to prove
the given properties. In addition, Kind 2 is able to find minimal sets of
design constraints, known as Minimal Cut Sets, whose violation leads the system
to an unsafe state. The computed information can be used for several purposes,
including assessing the quality of a system specification, tracking the safety
impact of model changes, and analyzing the tolerance and resilience of a system
against faults or cyber-attacks. We describe these new capabilities in some
detail and report on an initial experimental evaluation of some of them.
