What is AS4? The bridge between traditional EDI and API-native B2B integration.

B2B integration goes well beyond the world of IT: processes such as order fulfillment, delivery, invoicing, or payments affect your business directly. These traditionally EDI-driven processes play a role in everything from revenue and expenses to risk management or compliance, but they are also changing with the arrival of newer technologies.

As I’ve discussed in a previous article, we see continued growth for EDI as it increasingly coexists with APIs, which are becoming more and more critical to B2B integration. And AS4 acts as the bridge from traditional, mainly, EDI-driven flows to future API-native B2B integration.

Let’s give a definition for AS4 and look at how it works, as well as why this protocol is helping to bridge heritage and new technologies to keep businesses running 24/7 as they seek to modernize and improve processes.

What is AS4?

AS4 (Applicability Statement 4) is an interoperability protocol that simplifies and standardizes the use of web services for B2B data exchange and integration. It is a modern XML-based SOAP communication protocol, widely adopted by the industry in recent years to support various modern B2B/EDI integration use cases.

AS4 can be described as continued development of AS2 – a known standard to transfer EDI and other data that’s still one of the most widely adopted messaging standards in the world. Compared to AS2, AS4 provides more agility and reliability for the modern B2B ecosystem thanks to SOAP-driven exchanges, XML, metadata, and WS-Security.

By now, you may have recognized SOAP from the world of APIs (SOAP APIs). AS4 uses SOAP as its messaging protocol between different systems and organizations, similarly to how modern APIs use SOAP as a communication protocol. At the same time, on a functional level, AS4 is similar to EDIINT (EDI via Internet) – a known EDI protocol. This is how AS4 can act as a bridge from traditional EDI to modern API-driven processes.

What are important characteristics of AS4?

AS4 was created based on ebXML (Electronic Business XML) in 2013 to simplify the use of ebXML Messaging Services by narrowing its application options and following the just-enough design principle.

Being an open standard, AS4 ensures that there will be no vendor locking. You can procure solutions in a competitive environment where vendors are encouraged to innovate continuously.

AS4 meets the requirements expected of any modern B2B protocol:

• Automation: AS4 allows the exchange of structured and unstructured data, as well as metadata. AS4 allows receivers to reroute messages and provides multiple mechanisms to correlate messages within a particular flow.
• Reliability: in case of a network disturbance, the message will be resent. AS4 ensures that a message is received once – and only once – which means that received duplicates are detected and eliminated.
• Security: the message cannot be imperceptibly modified during transit, 3^rd parties cannot access the data, and neither sender nor receiver can deny having sent or received a message.

Why SOAP and not REST as a basis for AS4?

In recent years, developers have favored REST over SOAP, particularly when it comes to web and mobile applications, and the use of REST continues to grow. The newer technology has accompanied the explosive growth of APIs because it’s flexible, lightweight, and easy to learn.

An important distinction, however, is that REST is a set of instructions that each developer can use differently, while SOAP is a well-defined, standard protocol.

SOAP is a more complex concept and usually requires more time to implement. But its standardized set of rules is particularly well-suited to enterprise applications, where standardization and continued control are key.

This is why you’ll see REST as a clear favorite in the latest IoT applications, whereas SOAP tends to be favored when it comes to enterprise IT applications where security, interoperability, and transaction compliance are a must.

Because AS4 was designed as a standard for secure and reliable B2B transactions, the choice of SOAP was logical.

The value of AS4

Because AS4 is based on SOAP, it provides additional benefits to users compared to AS2: it is more compatible with a common enterprise IT ecosystem because many organizations use these technologies for their integration and operational processes. Extending the use of these technologies for external integration becomes a very natural, seamless operation.

It’s also possible to add metadata to AS4 messages, beyond simple data exchanges. You can transport any type of payload: XML, JSON, EDI, HL7, binary and ASCII, and so on. You can also carry multiple payloads if needed.

Finally, security is based on WS-Security, an extension to SOAP specification. WS-Security defines a framework for protecting the integrity, confidentiality, and authentication of each AS4 message. WS-Security describes how to encode security tokens and attach them directly to the message, enhancing traditional channel-based security mechanisms such as HTTPS.

As stated earlier, AS4 is a next-generation protocol of the EDIINT – AS2 standard. From a functional point of view, it inherits its capabilities, but AS4 has important differentiators:

• AS4 is a modern version of AS2, based on technology standards that are aligned with the modern IT ecosystem of enterprises: SOAP, API-communication, Web Services, cloud convergency, etc.
• AS4 allows for SOA (Service-Oriented Architecture), not only document interchange. This means you can extend your SOA to reach out to your ecosystem.
• AS4 allows for a push, as well as for the pull. This means that applications that are not always online, that do not have a permanent IP address or that is behind a firewall to connect occasionally and pull available messages.

To summarize, AS4 can be seen as a superset of AS2. It’s a protocol that satisfies the needs of the modern market, fits the IT landscape of enterprises, and provides the needed level of security, resiliency, and agility.

AS4 adoption will continue to grow worldwide

AS4 is set to last for two decades. It has stood the test of time, and today is widely adopted by B2B and B2G markets. Even though REST/JSON communication is very popular these days, governments and enterprises continue to bet on AS4-driven processes, regulations, and mandates.

Each year, AS4 gains more and more interest from public and private organizations operating in B2G, B2B, and B2C markets. The following is a non-exhaustive list of communities who have adopted AS4:

• eDelivery eDelivery is one of the building blocks of the EU’s Connecting Europe Facility (CEF). It’s an AS4-driven program aimed at helping public administrations exchange data and documents with other public administrations, businesses, and citizens.
• ICS2 – Import Control System 2, an AS4-driven EU-wide mandate for air, maritime, road, and rail cargo businesses. (We discussed this recently in a webinar on B2B modernization.)
• e-Invoicing & PEPPOL. The EU (and beyond) mandates reporting of B2G and B2B transactions using AS4 and REST APIs.
• BPC – a B2B e-Invoicing initiative in the USA that’s also considering using AS4 as a communication protocol.
• ENTSOG – European Network of Transmission System Operators for Gas uses AS4 communication protocol. (See it in action with Axway and Equinor here.)
• EESSI – Electronic Exchange of Social Security Information. Driven by AS4, it speeds up exchanges between European social security institutions.
• e-CODEX provides easy access to cross-border justice for citizens, business, and legal professionals all over Europe. It uses AS4 communication.
• SuperStream – The Australian Government’s AS4-driven gateway streamlines the way employers make super contributions for their employees.

Trust proven experts with AS4 and any B2B integration needs

At Axway, we’ve seen the adoption of AS4 grow, both on the market and with our customers. It’s why our B2B Integration platform makes it possible to communicate effortlessly with all your partners by accommodating the standards and protocols they demand – be it EDIINT AS1, AS2, AS3, AS4, RosettaNet RNIF, OFTP, or ebXML ebMS.

We don’t just have a track record of supporting our customers through evolving messaging protocols: we’ve quite literally helped to define standards like AS2 and AS4.

What’s more, the Drummond Group – an independent agency that certifies software products and solutions such as for interoperability standards — uses our B2B Integration solution as a benchmark for all connectivity vendors.

Axway’s B2B Integration Platform experience offers security and speed, allowing you to streamline EDI and API flows and leverage value-added services such as e-Invoicing, PEPPOL, API management, and API-driven VAN.

Connect your enterprise to all your customers, suppliers, financial institutions, and regulatory bodies and quickly communicate with them whenever and wherever you need to, with the highest levels of security and availability.