It's covered in the preamble to Chapter 15 of the EJB 3.1 spec.
"This chapter describes the interoperability support for accessing an enterprise bean through the EJB 2.1 remote client view from clients distributed over a network, and the distributed interoperability require- ments for invocations on enterprise beans from remote clients that are Java Platform, Enterprise Edition (Java EE) components. Distributed Interoperability is not defined for the EJB 3.x remote client view."
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