VoiceXML is designed for creating audio dialogs that feature synthesized speech, digitized audio, recognition of spoken and DTMF key input, recording of spoken input, telephony, and mixed initiative conversations.
VoiceXML (VXML) is the W3C's standard xml format for specifying interactive voice dialogues between a human and a computer. It allows voice applications to be developed and deployed in an analogous way to html for visual applications. Just as HTML documents are interpreted by a visual web browser, VoiceXML documents are interpreted by a voice browser.
Typically, http is used as the transport protocol for fetching VoiceXML pages. Some applications may use static VoiceXML pages, while others rely on dynamic VoiceXML page generation using an application server like tomcat, weblogic, iis, or websphere.
Historically, VoiceXML platform vendors have implemented the standard in different ways, and added proprietary features. But the VoiceXML 2.0 standard, adopted as a W3C Recommendation on 16 March 2004, clarified most areas of difference. The VoiceXML Forum, an industry group promoting the use of the standard, provides a conformance testing process that certifies vendors' implementations as conformant.
VXML's latest spec version is 2.1. VXML 3.0 is in the working draft stage for many years now.