Operators and functions for context

Context functions are used for complex event evaluation by a filter condition or an event rule condition.

Operators

Table 1. Operators for event context
Operator	Format	Returns a Boolean value of true if . . .
`event follows`	`this event follows variable1`	There is at least one previous occurrence of the event or action specified in `variable1`
`event follows after`	`this event follows variable1 after variable2`	There is at least one occurrence of the event or action specified in `variable1` after the date and time specified in `variable2`
`event follows before`	`this event follows variable1 before variable2`	There is at least one occurrence of the event or action specified in `variable1` before the date and time specified in `variable2`
`event follows within`	`this event follows variable1 within variable2`	There is at least one occurrence of the event or action specified in `variable1` within the duration specified in `variable2`
`event is present`	`this event is present`	The event has previously occurred
`event is present after`	`this event is present after variable1`	The event occurred after the date and time specified in `variable1`
`event is present before`	`this event is present before variable1`	The event occurred before the date and time specified in `variable1`
`event is present within`	`this event is present within variable1`	The event occurred within the time period (duration) specified in `variable1`

Functions

Table 2. Functions for event context
Function name	How function is expressed	Returns	`Variable1` can be	`Variable2` can be
`event or action occurs`	all occurrences of `variable1`	The number of times the referenced event or action in `variable1` has occurred in the context. The number includes the current instance.	`event` or `action`
`event or action occurs after`	all occurrences of `variable1` after `variable2`	The number of times the referenced event or action in `variable1` has occurred in the context after the date and time specified in `variable2`. The number includes the current instance.	`event` or `action`	`date`
`event or action occurs before`	all occurrences of `variable1` before `variable2`	The number of times the referenced event or action in `variable1` has occurred in the context before the date and time specified in `variable2`. The number includes the current instance.	`event` or `action`	`date`
`last occurrence of an event`	last occurrence of `variable1`	The date and time for the last occurrence of the event or action in `variable1`.	`event` or `action`
`last occurrence of an event is null`	last occurrence of `variable1` is null	The specified event or action has never occurred in the context.	`event` or `action`
`last occurrence of an event is not null`	last occurrence of `variable1` is not null	The specified event or action has occurred in the context.	`event` or `action`
event or action occurs within `duration`	past occurrences of `variable1` within `variable2`	The number of times the referenced event or action in `variable1` has occurred in the context in the duration specified in `variable2`. The number excludes the current instance.	`event` or `action`	`duration`
`event occurs after`	all occurrences of this event after `variable1`	The number of times the referenced event in the event rule has occurred in the context after the date and time specified in `variable1`. The number includes the current instance.	`date`
`event occurs before`	all occurrences of this event before `variable1`	The number of times the referenced event in the event rule has occurred in the context before the date and time specified in `variable1`. The number includes the current instance.	`date`
event occurs in `duration`	past occurrences of this event within `variable1`	The number of times the event referenced in the event rule has already occurred in the context in the duration specified in `variable1`. The number excludes the current instance.	`duration`

Note: When a time-delayed event rule is evaluated, or a time-delayed action is fired, the event or the action is no longer the current instance, and is included in the count when evaluating "past occurrences" functions.

How occurrences are counted

Each time an event enters the context, it is counted. For example, the first time it enters the context, the occurrences count is 1 and the second time it enters, the occurrences count is 2. Conditions must be created accordingly, as shown in the following examples:

Table 3. How occurrences are counted.
This condition	Value
all occurrences of `this event` is more than 0	`true` as soon as the first instance of `this event` enters the context, and continues to be `true`.
all occurrences of `this event` is 1	`true` when the first instance of the event enters the context, but is not `true` again.
all occurrences of `this event` is more than 1	`true` when the second instance of the event enters the context, and continues to be `true`.
all occurrences of `this event` is 0	Never `true`.