7. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method, the method comprising: receiving, from a mobile device, event data derived from contextual data collected using detectors that detect a physical context surrounding the mobile device; modifying a context graph that stores facts and assertions about a user's behavior and interests using the event data; in response to determining that there exists a registration for notification of changes that matches the modification to the context graph, sending a notification of context graph change to a recommender.
12. The non-transitory computer-readable storage medium of claim 7 , further comprising: receiving bulk upload of event data through an event posting interface; and modifying the context graph based on the received bulk upload event data.