Discussion on modeling reachability properties in TLA⁺ raises questions about TLC's capabilities

The ongoing discussion highlights the complexities involved in expressing reachability properties within TLA⁺. Current capabilities of TLC do not allow for comprehensive checks of these properties, which can limit the effectiveness of TLA⁺ in modeling certain behaviors. The community is exploring potential solutions to this challenge.

One of the key points raised is that while TLC can check basic reachability properties, it currently lacks the capability to verify more complex reachability scenarios. The introduction of the _POSSIBLE operator is a step toward addressing this, but it does not fully resolve the need for a more robust reachability check from every system state.

The proposed backward reachability algorithm could enhance TLC's functionality significantly by allowing it to identify whether a state can be reached from any initial configuration. However, the feasibility of implementing this algorithm remains uncertain, and its success hinges on careful integration with existing TLC processes to avoid disruptions.

As engineers continue to rely on TLA⁺ for system specification and verification, understanding these limitations and potential workarounds is crucial. The conversation around reachability properties can drive improvements in TLA⁺ and its associated tools, ultimately benefiting those who depend on these formal methods for reliable systems.