- Location as a context: The location is used to group events together as they serve as input for any event processing function such as: aggregation of pattern matching.
- Location as enabler for spatial patterns: The locations of events is used in the function that determined whether a certain pattern is being matched.
Note that these two roles of locations are orthogonal.
An example for the first role: count all the police vehicles that are within 5 KM from a crime scene, where there are periodic events that identify the location of the police vehicles using GPS devise. In this case, location is done to find out which events are "in context", and the event processing function itself is a simple aggregation (count).
An example for the second role: A certain company experienced over one week, 20 events of breaking into employees houses, it an an attempt to figure out whether this is a work of a single person, the pattern that is matched is: the maximal distance between two breaking in events that occurred within a single night is less than 15KM. In this case the context is not spatial, since the events involved are determined by time ("a single night") and segmentation ("events related to houses of employees"), but the pattern that we are looking for is spatial, since it involves location.
As said, time can also play in the context role, in the pattern role, in both, or in none.
More on spatial event processing - later.