Definition
AS4 (Applicability Statement 4), also called EDIINT AS4, provides secure B2B document exchange using web services. It was developed within the OASIS ebXML Messaging Services Technical Committee. AS4 gives organizations an entry point to reuse internal SOA-style platforms for external B2B messaging while adopting standardized web-services mechanics. European aerospace and other communities have proposed AS4 for ebXML-related B2B traffic.
AS4 did not appear in isolation: it continues a line of B2B standards from ebXML (2002) through OASIS standardization (2013) and ISO recognition. As an open standard, it reduces vendor lock-in and supports competitive sourcing.
What AS4 must deliver
- Automation — Structured and unstructured payloads, with metadata for routing and correlation across messages.
- Security — Integrity (tamper detection), confidentiality, and non-repudiation so senders and receivers cannot plausibly deny participation.
- Reliability — Resend after transient failures; detect and eliminate duplicate delivery.
How AS4 differs from AS2
AS4 is based on SOAP and web services, whereas AS2 rides on HTTP with a simpler peer model. That often makes AS4 a natural extension where enterprises already run SOAP/WS-* internally.
- Modern stack alignment — SOAP, REST-adjacent patterns, and enterprise integration tooling.
- Service-oriented exchanges — Not only document interchange; supports SOA-style interactions with trading networks.
- Push and pull — Partners that are not always online, lack a fixed IP, or sit behind firewalls can pull messages when connected.
- Superset positioning — Often described as a next-generation complement to AS2 for large communities and mixed partner maturity.
AS4 can carry many payload types: traditional EDI, XML, JSON, binary, and more. Security builds on WS-Security; transport security uses TLS over HTTP.
Messaging standard (summary)
- Interoperability — Profile builds on OASIS ebMS 3.0.
- Security — WS-Security subset for non-repudiation and confidentiality.
- Reliability — Receipt/signal messages support single delivery semantics.
- Payload independence — EDI, XML, and other formats.
Messaging service handler (MSH)
The MSH sets up AS4 exchange with the remote access point on send or receive, conforming to AS4 specifications and handing off to internal business applications.
Message types (ebMS 3.0 profile)
- User message — Business payload between applications.
- Signal messages — Support non-repudiation and reliability: Receipt (receiver processed the incoming message), Error (receiver could not parse/process the message), and Pull request (supports pull exchange patterns).
Adoption
AS4 is used where SOA-style B2B is required — retail, health, utilities, and regulated networks. Examples include PEPPOL, e-CODEX, ENTSOG, EPREL, JEITA (Japan), Australian Superstream pensions, and IATA cargo e-business. European programs have production use across multiple countries; PEPPOL has also spread to New Zealand, Australia, and beyond.