Appendix A. Definitions
This appendix is a glossary of the special terms we use in this book.
The absence pattern is satisfied when there are no participant events. The matching set is empty (see section 9.2.1).
An Aggregate EPA is a Transformation EPA that takes as input a collection of events and creates a single derived event by applying a function over the input events (6.2.4).
The all pattern is satisfied when the participant event set contains at least one instance of each event type that is mentioned in the relevant event types list. The pattern matching set is made up of the event instances (one for each relevant event type) that cause the pattern to be satisfied (9.2.1).
The always pattern is satisfied when the participant event set is non-empty and all the participant events satisfy the always pattern assertion. If the pattern is satisfied, the matching set is the entire participant event set (9.2.4).
The any pattern is satisfied if the participant event set contains an instance of any of the event types in the relevant event types list. The pattern matching set consists of the event instance that causes the pattern to be satisfied (9.2.1).
The availability of a system is the percentage of the time its users perceive it to be functioning (10.2.2).
The average distance pattern is satisfied when the average distance of all the participant events from a given point satisfies the average distance threshold assertion (9.3.3).