As4

AS4, or Applicability Statement 4, is an OASIS standard for the secure and reliable exchange of business data over the internet. It provides a Web Services-based profile of the ebXML Messaging Service (ebMS) 3.0 that enables interoperable business-to-business messaging using SOAP over HTTP or HTTPS. AS4 is designed to support automated, auditable, and end-to-end communications between trading partners, independent of platform or vendor.

Key features include security, reliability, and interoperability. Security is achieved through WS-Security, XML Signatures, and XML Encryption to ensure message integrity, authentication, confidentiality, and non-repudiation of origin and receipt. Reliability is provided by ebMS 3.0 messaging semantics, including guaranteed delivery, duplicate detection, persistent stores, and structured acknowledgments. Interoperability is facilitated by a stable profile and the use of standard Web Services bindings, with support for attachments and various transport configurations.

AS4 also defines collaboration mechanisms such as collaborations Agreements (CPAs) to describe partner capabilities and expected behavior, enabling consistent processing rules across participants. The standard is used by many B2B networks and software vendors, and is a core protocol in Europe’s PEPPOL e-procurement and e-invoicing infrastructure, among others.

Governance and status: AS4 is maintained by OASIS as an official profile of ebMS 3.0. It is designed to be transport- and platform-agnostic, promoting interoperability across diverse systems for cross-border and domestic business data exchange.