VoiceXML Specification Support
The level of and conformance to the VoiceXML specification are important considerations because the supported features determine the upper bounds of the application to be developed. Additionally important is how a particular vendor has interpreted the specification due to the existence of platform-specific VoiceXML elements. At the time of writing, the VoiceXML Forum Conformance Subgroup planned to publish a conformance test suite for the VoiceXML 2.0 specification. In terms of the evolution of the specification itself, as of this writing, the VoiceXML 2.0 specification is progressing from Working Draft toward Recommendation.
Compare the VoiceXML specification evolution paths for several of the potential vendors. For platform-specific elements, test the elements on any available hardware platform to understand the differences between the implementations. Some cases might require obtaining accounts on portals such as Nuance, IBM, VoiceGenie, or TellMe.