Some commands interrupt the browser. For instance to request a list of hypertext links occurring in the current section of the document. Other commands are given when the browser prompts for input, for example, to select an option from a menu in a form. To increase the robustness of speech recognition, voice browsers take advantage of contextual clues provided by the author. This allows the recognition engine to focus on likely utterances, improving the chances of a correct match.
Work is needed to specify how such contextual clues are represented.
Speech synthesis is driven by dictionaries, falling back for unknown words on rules for regular pronunciation. High quality speech synthesis is possible if the author can extend the dictionary resident in the browser. This should be practical without the author being a qualified phonetician with a deep understanding of terms such as Labiodental , and Alveolo-palatal fricatives . Work is needed to establish a simple means for authors to specify how particular words should be spoken. Alternate Media Speech synthesis is not as good as having an actor read the text.