1. A method performed by a computer server for inferring location context categories for a set of mobile users having at least two members, comprising: for each mobile user in the set, obtaining at least one location context category; and applying multi-user collaborative machine learning with an objective function to the at least one location context category for each mobile user in the set to infer a single refined location context category for each mobile user in the set to form a matrix.
1. A method performed by a computer server for inferring location context categories for a set of mobile users having at least two members, comprising: for each mobile user in the set, obtaining at least one location context category; and applying multi-user collaborative machine learning with an objective function to the at least one location context category for each mobile user in the set to infer a single refined location context category for each mobile user in the set to form a matrix. 3. The method of claim 1 , wherein said obtaining step comprises: for each mobile user in the set, sending a respective query to one or more mobile web applications that return the at least one location context category applicable to a submitting one of the mobile users responsive to the uncertain mobile device location data specified in the respective query; and for each mobile user in the set, receiving the at least one location context category from the mobile web application responsive to the respective query.