Halt
You can use the Halt function to halt the current rule engine execution. The Halt function takes one parameter of type Boolean. If you specify the value for the parameter as true, the rule engine also clears the agenda that contains the pending candidate rules.
The Policy.Execute method is basically a wrapper around the RuleEngine.Execute method. It has code similar to the following code:
RuleEngine.Assert(facts);
RuleEngine.Execute();
RuleEngine.Retract(facts);
If you use the Policy.Execute method to execute a policy, the rule engine returns control to the Policy.Execute method when the Halt function is executed. The Policy.Execute method retracts the facts and returns control to the caller. Therefore, the halted policy execution cannot be resumed in this case. The same thing happens when you use the Call Rules shape to invoke the policy.
However, if you use the RuleEngine.Execute method directly to execute the policy, you can resume the halted policy execution with the next pending rule firing by simply calling RuleEngine.Execute again (provided you did not retract any objects needed between the two calls). The sample code for resuming the halted policy execution is as follows:
//assert facts into working memory of the rule engine instance
RuleEngine.Assert(facts);
//execute the policy
RuleEngine.Execute();
//policy invokes the Halt method when executing actions.
//control is returned to here when the Halt method is invoked
//when engine is halted do the following
//Add your code here
//To resume the halted rule engine execution
RuleEngine.Execute();
//retract or remove facts frm the working memory of the rule engine
RuleEngine.Retract(facts);
Note that the Policy.Execute method caches the rule engine instances for better performance. When you use the RuleEngine.Execute method directly, the rule engine instances are not cached.