When you create a rule you must also specify the trigger for the rule. The options available are:
Run once every page load
Run on page load and every X seconds, with an optional maximum limit
Run on change of specified JavaScript variable
When using these options, you can specify a value for the items in bold.
The configuration options selected define when the rule runs within the rule evaluation cycle.
Before describing the rule evaluation cycle, it is important to understand the difference between rule evaluation and rule execution.
Rule evaluation checks whether or not a rule is available for execution. Rule evaluation involves checking all the conditions associated with a rule to see whether they return a value. If all of the conditions are evaluated and return a true or false value, then the rule can be executed. If they do not return a true or false value, then the rule will not be executed and the rule will be evaluated again during the next rule evaluation cycle.
Rule execution occurs when all of the conditions associated with a rule have been evaluated and return a true or false value. The rule then performs the appropriate actions associated with the rule. If the evaluation returns a true value then the true actions are performed, and if the evaluation returns a false value then the false actions are performed.
There are three stages in the rule evaluation cycle during which rule evaluation and execution are carried out.
Evaluation Cycle 0
This stage happens on the server side just after page load. This stage removes all rules that do not apply to the current visitor’s web page.
Evaluation Cycle 1
This stage happens on the client side immediately after the response from Evaluation Cycle 0. All of the rules configured to run on page load are now evaluated and executed according to their evaluation order.
Evaluation Cycle 2+
This stage covers the evaluation and execution of all rules that are configured to run after Evaluation Cycle 1. These rules may be configured to run at set intervals or when a certain event occurs, so rule evaluation order may not be strictly followed during this cycle. Any rules configured to run at the same time are still evaluated and executed according to their evaluation order.
