A scalable access filter that is used together with others like it in a virtual private network to control access by users at clients in the network to information resources provided by servers in the network. In one aspect the method of forming a resin comprising the steps of: providing an aldehyde-cross-linking agent condensate obtained by reacting a volatile aldehyde with a cross-linking agent; providing a non-volatile aldehyde; and combining the aldehyde-cross-linking agent condensate and the non-volatile aldehyde, thereby forming the resin. Moreover, there is provided a storage frame with at least a machine readable label from which information regarding the storage device are read out from the machine readable label, which is attached to the storage device, at least before the storage frame is moved into the operating range of the robotic device. This deferred assignment of an index key until commit time means that the index key can be used to search for messages having the particular attribute without any possibility of identifying messages for retrieval before the messages have been committed. This delayed response prevents the external host device from pausing before attempting subsequent communication requests.