A rule pattern is the representation of an event correlation situation (such as a threshold condition or duplicate event detection). The Active Correlation Technology rule language defines the following rule patterns: collection, computation, duplicate, filter, sequence, threshold, and timer.
The pattern of a rule is matched when the situation that is defined by the rule occurs. When the pattern is matched, the rule concludes its processing by taking the appropriate rule response actions. While a rule is active, the rule pattern can be matched multiple times.
Rules that are defined by the filter pattern are the only stateless rules in the rule language. All other rules are stateful.