1. A 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.
1. A 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. 3. The method of claim 1 , wherein the event data includes high-level event data generated by the mobile device from contextual data.