What is the difference between VoiceXML and WAP?

Kenneth Liu

WML (Wireless Markup Language) is basically a simplified lightweight version of HTML which is used to display web pages on small mobile phone displays. WAP is to HTTP as WML is to HTML. A WML/WAP browser is embedded in the phone hardware to display the pages.

VoiceXML is used to create voice enabled applications for use with any regular phone. These applications often take the form of phone trees ("press 1 to do this, press 2 to do that") but can use ASR (automated speech recognition) to recognize spoken responses in addition to the normal touch tones. VoiceXML can also be used to do TTS (text to speech) instead of using prerecorded content. VoiceXML documents require an interpreter which normally runs on a powerful server.

VoiceXML and WAP are often mentioned in the same context because they are both seen as ways of accessing the Web using a wireless device. With WAP, the screen is used to display the content; with VoiceXML, TTS is used to play the content aloud.