Apache AXIS is an implementation of the SOAP ("Simple Object Access Protocol")
submission to W3C.

From the draft W3C specification:

SOAP is a lightweight protocol for exchange of information in a decentralized,
distributed environment. It is an XML based protocol that consists of three
parts: an envelope that defines a framework for describing what is in a message
and how to process it, a set of encoding rules for expressing instances of
application-defined datatypes, and a convention for representing remote
procedure calls and responses.

This project is a follow-on to the Apache SOAP project.