1. A method for controlling access to functions available to respective ones of a plurality of user devices, comprising: receiving service requests from the user devices; allowing or disallowing each of the user devices to access the respective requested function based on an application of pre-defined matching rules for matching access policies of the respective user devices with a respective representation of an environment for each of the user devices, each of the representations being based on information obtained from updates periodically received from the respective user devices, the information including state information concerning a physical environment of the respective user devices obtained from one or more sensors associated with the respective user devices.