Open Enum

An Open Enum is an element where a number of valid values are defined within this specification, but other values should not be rejected as invalid by any system other than the final message destination. Open Enums provide a mechanism for a client and final destination server to communicate with values that may be known to both endpoints but not to all intermediate servers that route the message. Open Enums are typically used for elements related to system message processing and have been defined as open to support extensibility and customization of the specification.