Section 6.4.1. of the Core Specification states the "ebMS Errors in addition to those specified here may be added by creating new errorCode values. The value of the errorCode attribute must begin with the five characters "EBMS:". "

It is not cleaar who may add these error codes. One obvious audience are specification authors, and the Part 2 and AS4 specifications define additional errors. However, it is not explicitly stated that there errors are not to be used by implementers. It would be undesirable if vendors start using other EBMS:* codes with proprietary semantics. EBMS:0004 is a catch-all error, and there is ErrorDetails in which they can put any sub-codes or other additional information.