1. A computer-implemented method operable on a device comprising hardware including memory and at least one processor, the method comprising: (A) receiving, at a service running on said hardware, invalidation information, the invalidation information comprising one or more invalidation commands, wherein at least one of said one or more invalidation commands comprises at least one group invalidation command that specifies a group of resources, wherein said at least one group invalidation command may relate, at least in part, to resources not currently stored on said service; (B) determining whether said invalidation information relates to information not currently stored on said service, and, based on said determining, (B)(1) when said invalidation information relates to information not currently stored on said service, maintaining on said service at least some of said invalidation information that relates to said information not currently stored on said service; and (C) said service using said maintained invalidation information to prevent subsequent use of a version of information not currently stored on said service.