Applicability Statement 4
The AS4 profile of eDelivery is the AS4 Usage Profile defined by eSENS based on the AS4 Profile of ebMS3 OASIS Standard. AS4 itself is based on other standards, in particular on OASIS ebXML Messaging Services, which in turn is based on various Web Service specifications.
Definition from https://ec.europa.eu/cefdigital/wiki/display/CEFDIGITAL/CEF+Glossary