WMI Query Language (WQL) is a dialect of SQL. WQL has many extensions that support Windows Management Instrumentation (WMI) event subscriptions. For example, the WITHIN keyword sets the interval in seconds that defines the accuracy of the event detection that the consumer expects. The Common Information Model Object Manager (CIMOM) uses that number as the polling interval to detect changes if the event doesn’t have a provider. You can combine the WITHIN keyword with GROUP BY and HAVING clauses to specify simple aggregations of similar events to achieve a filtering effect. Another extension important for event subscriptions is the ISA keyword. ISA lets you subscribe to changes of specific classes of managed elements. Using WQL, the event filter can define the type of event and the specific conditions under which CIMOM delivers the event to the consumer.