Address the issue in version 2

Oct 13, 2025 by wbrum.org 126 views

Introduction

In the context of Publicodes, a rule evaluation system, a critical issue arises when a cycle is detected during runtime. This cycle is "suppressed" by evaluating the rule to undefined, which can lead to unpredictable results. The problem lies in the fact that the rule evaluated to undefined is the first one that occurs twice in the evaluation stack, making it dependent on the start of the cycle. This article delves into the problem, its implications, and a proposed solution.

Problem

When a cycle is detected in Publicodes, the evaluation system suppresses it by setting the rule to undefined. However, this approach has a significant flaw. The rule evaluated to undefined is the first one that occurs twice in the evaluation stack. This means that the value of the rules involved in the cycle can change depending on the order in which they are evaluated. For instance, in a cycle a -> b -> c -> a, the values of a, b, and c might differ based on which rule is evaluated first.

To illustrate this issue, consider a simple example:

Rule a depends on b and c.
Rule b depends on c and a.
Rule c depends on a and b.

If the evaluation starts with a, the value of a will be determined based on the values of b and c. However, if the evaluation starts with b, the value of b will be determined based on the values of c and a. This creates a dependency on the start of the cycle, leading to unpredictable results.

Solution

A potential solution to this issue has been proposed in issue #637. However, this solution is currently a dead end due to the complexity of the problem. The issue is significant, as it may potentially break the current evaluation model. Therefore, it is recommended to address this issue in version 2 of Publicodes.

Test Files

The test files for this issue can be found in the pull request #637 on the Publicodes GitHub repository. The relevant code snippet is located in the diff file #diff-2f3eabe8123c43f972eec56143504d5c3e88106fe8af31b80b6bf192248b785c.

Conclusion

The issue of non-idempotent evaluation in the presence of cycles is a critical problem in Publicodes. The current approach of suppressing cycles by setting rules to undefined leads to unpredictable results. A proposed solution has been identified, but it requires significant changes to the evaluation model. Therefore, it is recommended to address this issue in version 2 of Publicodes.

Future Work

To resolve this issue, further research and development are required. The following steps can be taken:

Re-design the evaluation model: A new evaluation model should be designed to handle cycles in a more robust and predictable manner.
Implement the new model: The new evaluation model should be implemented in Publicodes, ensuring that it is backward compatible with the existing codebase.
Test the new model: Thorough testing should be performed to ensure that the new evaluation model handles cycles correctly and produces predictable results.

By addressing this issue, Publicodes can provide a more reliable and predictable evaluation system, which is essential for its users.

Recommendations

Based on the analysis of this issue, the following recommendations can be made:

Address the issue in version 2: The issue of non-idempotent evaluation in the presence of cycles should be addressed in version 2 of Publicodes.
Re-design the evaluation model: A new evaluation model should be designed to handle cycles in a more robust and predictable manner.
Implement the new model: The new evaluation model should be implemented in Publicodes, ensuring that it is backward compatible with the existing codebase.
Test the new model: Thorough testing should be performed to ensure that the new evaluation model handles cycles correctly and produces predictable results.

Q&A

Q: What is the problem with evaluating rules in Publicodes when a cycle is detected?

A: When a cycle is detected in Publicodes, the evaluation system suppresses it by setting the rule to undefined. However, this approach has a significant flaw. The rule evaluated to undefined is the first one that occurs twice in the evaluation stack. This means that the value of the rules involved in the cycle can change depending on the order in which they are evaluated.

Q: What is the impact of this issue on the evaluation results?

A: The issue of non-idempotent evaluation in the presence of cycles can lead to unpredictable results. The values of the rules involved in the cycle can change depending on the order in which they are evaluated. This can cause the evaluation results to be inconsistent and unreliable.

Q: How can this issue be resolved?

A: A potential solution to this issue has been proposed in issue #637. However, this solution is currently a dead end due to the complexity of the problem. The issue is significant, as it may potentially break the current evaluation model. Therefore, it is recommended to address this issue in version 2 of Publicodes.

Q: What are the steps to resolve this issue?

A: To resolve this issue, the following steps can be taken:

Re-design the evaluation model: A new evaluation model should be designed to handle cycles in a more robust and predictable manner.
Implement the new model: The new evaluation model should be implemented in Publicodes, ensuring that it is backward compatible with the existing codebase.
Test the new model: Thorough testing should be performed to ensure that the new evaluation model handles cycles correctly and produces predictable results.

Q: Why is it recommended to address this issue in version 2 of Publicodes?

A: The issue of non-idempotent evaluation in the presence of cycles is significant, and addressing it in version 2 of Publicodes will ensure that the evaluation model is robust and predictable. This will provide a more reliable and consistent evaluation system for users.

Q: What are the benefits of resolving this issue?

A: Resolving this issue will provide several benefits, including:

Improved reliability: The evaluation model will be more robust and predictable, reducing the likelihood of inconsistent results.
Increased consistency: The evaluation results will be more consistent, making it easier for users to rely on the output.
Better user experience: Users will have a more reliable and consistent evaluation system, making it easier to use and integrate with other tools.

Q: How can users contribute to resolving this issue?

A: Users can contribute to resolving this issue by:

Reporting issues: Users can report any issues they encounter with the current evaluation model.
Providing feedback: Users can provide feedback on the proposed solution and suggest alternative approaches.
Testing the new model: Users can test the new evaluation model and provide feedback on its performance.

By working together, users and developers can resolve this issue and provide a more reliable and consistent evaluation system for Publicodes.