VoiceXML Review - Columns

Volume 1, Issue 8 - August/September 2001

Caching and Prefetching in VoiceXML

By Rob Marchand

(Continued from Part 1)

Where Does Caching Work?

The following tags support the caching and fetchhint attributes:

audio
choice
dtmf
goto
grammar
link
object
script
subdialog
submit

By applying the two attributes to these VoiceXML elements, the application author can exercise fine-grained control over how and when things are fetched.

The developer can also control caching and prefetch using the following properties

caching - this property can be set to safe or fast;
audiofetchhint, documentfetchhint, grammarfetchhint, objectfetchhint, scriptfetchhint - these properties can have the values safe or prefetch;

The various fetchhint properties apply to the related types of fetches (e.g., grammarfetchhint applies to grammar file fetches only).

If a tag has the attribute applied, then the caching is applied to that element only. If no caching attribute is present, then the tag inherits the value derived from the innermost relevant caching property.

Caching in VoiceXML 2.0

VoiceXML 2.0 isn't yet a public working draft, but should be soon. Suffice it to say that the Voice Browser Working group has made some improvements in the area of caching, including giving it a better mapping to HTTP 1.1, and giving the developer tighter control over when web fetches occur (and, more importantly, when they don't!).

What's Next?

Well, we've finally gotten caching out of the way. Next month, we're going to look the <transfer> tag, and, if we have space, the <record> tag. In the meantime, enjoy what's left of the summer!

Watch future issues of VoiceXML Review for more articles about getting started with VoiceXML.

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