Policy Conflict Resolver

A policy evaluator that focuses on conflict resolution when multiple applicable policies provide conflicting results. The interface and input/output is based on those of the ODRL Evaluator.

The core class is the ConflictEvaluator which has the same interface as the above-mentioned ODRL Evaluator and is instantiated with 3 parameters:

1. A PolicyExtractor which consumes a set of Quads containing one or more policies, and for every policy it detects, returns an array of Quads containing only the relevant Quads for that policy. This library provides an implementation for default ODRL in the OdrlPolicyExtractor.
2. Another Evaluator, such as the ODRL Evaluator. This Evaluator will be called for every Quad array returned by the previous step. The request and state arrays will remain unchanged.
3. A ConflictResolver that takes all the reports returned by the previous steps and generates a new report by applying a conflict resolution algorithm on those reports. This library provides several that can be chained together:
   • ActiveConflictResolver, which filters out inactive reports.
   • PriorityConflictresolver, which only keeps the reports of the policy rules with the highest priority. A priority can be given to a rule using the urn:example:custom:odrl:priority predicate.
   • DenyConflictResolver, which prioritizes prohibitions over permissions.

For example, a ConflictEvaluator can be initialized with the following code:

const extractor = new OdrlPolicyExtractor();
const source = new WrappedEvaluatorHandler(new ODRLEvaluator(new ODRLEngineMultipleSteps()));
const resolver = new ActiveConflictResolver(new PriorityConflictResolver(new DenyConflictResolver()));

const evaluator = new ConflictEvaluator(extractor, source, resolver);
evaluator.evaluate([], [], []);

The resulting report is expected to contain all the necessary information of why a decision was reached. For example, using the example classes described above with the data from the example run of the ODRL Evaluator repository, results in the following report:

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix report: <http://example.com/report/temp/>.

<urn:uuid:66b760b3-c9f8-4b5e-9810-900f296e6241> a report:ConflictReport;
    report:algorithm report:PrioritizeDeny, report:HighestPriority, report:OnlyActiveRules;
    report:conclusion report:Allow;
    report:reason <urn:uuid:3af49332-1fd5-42d1-9621-f3a6299ac457>;
    report:policyReport <urn:uuid:e5eba200-8faf-40df-adb0-106e12d2c231>.
<urn:uuid:e5eba200-8faf-40df-adb0-106e12d2c231> a report:PolicyReport;
    <http://purl.org/dc/terms/created> "2024-02-12T11:20:10.999Z"^^<http://www.w3.org/2001/XMLSchema#dateTime>;
    report:policy <urn:uuid:95efe0e8-4fb7-496d-8f3c-4d78c97829bc>;
    report:policyRequest <urn:uuid:1bafee59-006c-46a3-810c-5d176b4be364>;
    report:ruleReport <urn:uuid:3af49332-1fd5-42d1-9621-f3a6299ac457>.
<urn:uuid:3af49332-1fd5-42d1-9621-f3a6299ac457> a report:PermissionReport;
    report:attemptState report:Attempted;
    report:rule <urn:uuid:f5199b0a-d824-45a0-bc08-1caa8d19a001>;
    report:ruleRequest <urn:uuid:186be541-5857-4ce3-9f03-1a274f16bf59>;
    report:activationState report:Active.

Potential issues

Policy extraction

The OdrlPolicyExtractor splits policies by detecting individual rules. These are found by looking for the action and target relations of rules, and potentially making the cross product if these occur multiple times in the same rule. This has two potential issues:

1. In case a policy uses custom profile relations that could also indicate different rule instances, these will not be detected.
2. If the target and/or action are linked to the policy instead of the rule, the extractor will be unable to handle that.

ODRL focus

Currently, some components are still assuming too much that the input will be ODRL.

Components.js

This library supports Components.js configurations. See the config folder for examples.