The Rules OSID provides a means to evaluate rules and retrieve results. A Rule represents a something that can be executed and can be organized into Engines. The rule evaluation accepts a Condition that is used to supply input conditions to the rule engine.

The Rules OSID does not define a means for authoring rules. Definitions exist for evaluating, examining and organizing rules. A Rule is identified by an Id such that a consumer wishing to evaluate a rule must have knowledge of the Rule Id along with the expectations of data (recod Type ) required in the Condition. The Rule also implies the structure of the Result, which can be a simple boolean value or another structure defined in a Result Record.

Engines can be organized into hierarchies for federation. An engine that is a parent of another engine makes visible the rules of its children.

Example where the consumer executes a rule with knowledge of the Rule Id , ConditionRecord Type, and the meaning of the Result.

                         
                         
                         RulesSession session = manager.getRulesSession();
                         Condition condition = session.getConditionForRule(shouldIWearACoatRuleId);
                         if (!condition.hasRecordType(temperatureConditionRecordType) {
                             error ("temperature condition record not supported");
                         }
                         
                         TemperatureCondition temp = condition.getConditionRecord(temperatureConditionRecordType);
                         temp.setTemperature(28);
                         
                         if (session.evaluateRule(shouldIWearACoatRuleId, condition) {
                             putOnACoat();
                         }