Applicability Statement 3 (AS3)

AS3, or Applicability Statement 3, is a communication protocol used for the electronic exchange of business documents between trading partners. The protocol is designed to ensure the secure and reliable exchange of data between businesses and is commonly used in the context of Value-Added Networks (VANs). 

A VAN is a third-party service provider that acts as a mediator between trading partners, providing a secure and reliable network for the exchange of electronic data. AS3 is used as the communication protocol within this network, providing a standard way for businesses to send and receive electronic business documents, such as purchase orders, invoices, and shipment notices.