Excerpt: Early Adopter VoiceXML: VoiceXML with XSLT (HTML and WML)

Wrox Press Book - Early Adopter VoiceXML
Chapter 7, VoiceXML with XSLT (HTML and WML)

This chapter examines the use of the Extensible Stylesheet Language for Transformations (XSLT) as a tool for the generation of VoiceXML. I intend to illustrate a complete, end-to-end example of implementing a voice interface for a client-server database via XML and XSL. The case study will demonstrate the power of XSL for simultaneously delivering multiple interfaces to the same data by developing HTML and WML front-ends also.

Our case study takes us inside the rarified atmosphere of a fictional cash-strapped dot-com called MyRubberBands.com, purporting to be the "premier rubber bands site on the Internet". In the aftermath of the stock market meltdown, where our heroes saw their market valuation drop by over 95%, senior management, led by CEO Dr. Todd, has decreed that adding WML and voice functionality to the existing order status web site is do-or-die. MyRubberband's competitors have just rolled out their own WAP/voice access solution, and an all-out effort is necessary to catch up. Follow the programmers as they embark on their project to quickly roll out an equivalent capability.

Our development team have decided to implement an XSLT-based solution to the problem. XSLT is an XML-based language for transforming input structured according to one XML vocabulary to structured output in another XML vocabulary, or some general text form.

XSLT treats the document to be transformed as a set of nodes. An XSLT stylesheet defines a set of rules, or templates. When a template matches one of the nodes in the source document, the output structure given in the template is created in the transformed document. XSLT uses the W3C XPath specification language to query XML data. XPath is strongly analogous to SQL, and lets us specify complex rules to match nodes in a document.



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