"absent event" .
- There have no been any major financial transaction during the working day for the customer John Galt.
- The Pizza order has been received, but the delivery did not arrive within 40 minutes.
In these two examples we are looking for - things that did not happen within a certain context; the first example is the context of - "John Galt's financial activities within a single working day", the event that did not happen - "major financial transaction" is by itself a pattern that need to be defined and detected (say - a transaction with financial value of more than $10,000). The absence is on all time stamps that belong to the context - so the formal definition of the absence pattern of event e in context C is defined as : For context C, for all time-stamp t that belongs to the temporal extension of context C, event e does not occur in time-stamp t.