Recent work in extensible programming languages and operating systems by Redell, Lampson, Hewitt, and others coupled with developments in distributed computer systems motivates a study in models of the implementation of protection on tagged architectures. an extension of the notions of message and actor as discussed in previous work provides and abstract framework which may lead to the development of a suitable virtual machine. We wish to show that such a system provides a good framework for representation and protection of types, data, and procedures.