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. 4. The method of claim 1 , further comprising: receiving a query for context graph data from the recommender; and sending the context graph data to the recommender.