Aggregation operators

You can use aggregation operators over a collection of objects. Aggregation operators calculate the average, total, minimum, or maximum value of the numeric attributes in a collection of objects, or the number of objects in a collection.

Aggregation operators compute a value from a collection of values.

You cannot use aggregation operators in the action part of the rule.

Table 1. Aggregation operators
Operator	Description	Example
`the average <attribute> of <collection>`	Calculates the average value of an attribute in the collection of objects.	`if the average amount of all purchases is more than 500 then print "Gold customer."`
`the minimum <attribute> of <collection>`	Returns the minimum value of an attribute in the collection of objects.	`if the minimum amount of all purchases is at least 200 then print "eligible for loyalty card";`
`the maximum <attribute> of <collection>`	Returns the maximum value of an attribute in the collection of objects.	`if the maximum amount of all purchases is between 800 and 1000 then print "send 20% discount voucher";`
`the total <attribute> of <collection>`	Calculates the total value of an attribute in the collection of objects.	`if the total amount of all purchases is more than 1000 then print "too much spending.";`
`the number of <collection>`	Returns the number of objects in a collection. When this operator is applied to a collection that is defined by the `all` construct, the article is removed to improve readability.	`if the number of purchases is more than 100 then print "send 25% discount voucher";`

Example

if 
    the total amount of all purchase events,
        where the time of each purchase is during the last period of 1 week, is more than 1000
then 
    print "too much spending in 7 consecutive days.";