Abstract: In general, one aspect of the subject matter described herein can be embodied in methods that include the actions of: for each of a plurality of devices, perceiving, in relation to the device, one or more proximate devices, generating a record of the perception of the one or more proximate devices, receiving, from at least one of the one or more proximate devices, one or more records of respective prior perceptions of one or more devices in relation to the at least one of the one or more proximate devices, and providing, to another device that is not among the one or more proximate devices, (a) the record of the perception of the one or more proximate devices and (b) the one or more records of respective prior perceptions.