Web services may use SOAP over HTTP protocol, allowing less costly interactions over the Internet than via proprietary solutions like EDI/B2B. Besides SOAP over HTTP, web services can also be implemented on other reliable transport mechanisms like FTP. In a 2002 document, the W3C Web Services Architecture Working Group defined a Web Services Architecture, requiring a standardized implementation of a "web service." In this:
It [Web Service] has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the web service in a manner prescribed by its description using SOAP-messages, typically conveyed using HTTP with an XML serialization in conjunction with other web-related standards.
— W3C, Web Services Glossary