Main Page | See live article | Alphabetical index Application Exchange (APEX) was an early proposal to the IETF of a standard protocol for instant messaging. It was based on XML, but is no longer being considered for use. Today, SIP and SIMPLE, and XMPP are currently being discussed for us as an instant messagning protocol. Proponents of APEX have now mostly put their support behind XMPP as it is also based on XML. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.