January 27, 2021
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Excerpt: Early Adopter VoiceXML: VoiceXML with XSLT (HTML and WML)

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For a lot of applications, and for getting off to a quick start when processing XML, it is just the ticket — especially when you consider that XSLT is a relatively new technology so that processors should still have plenty of performance improvements possible. Use of an XSLT processor avoids the startup overhead of using a full parser API from a compiled language, making it more suited to dynamic web applications.

MyRubberBands.com — A Case Study

Our legacy database is implemented with MySQL, an open source client-server relational database management system. SQL code for the schema and a set of sample data is included in the code download for this book.

An XML schema is used to represent an export of the legacy database instead of a Document Type Definition (DTD) because the schema standard is now complete, and increasing numbers of developers will be looking for the extra power schemas offer, especially as new development tools become available. An excellent primer on schemas is available from the W3C at http://www.w3.org/TR/xmlschema-0/.

Scripts to export the database to XML format have been written using the Perl language, and the Data Base Interface (DBI) library. The Perl script shown was developed on Windows using Active State Perl, but should run on any platform, be it Windows or Unix. Many commercial databases, such as SQLServer 2000, are capable of exporting directly to XML, and so this step could be avoided entirely.

Business Requirements

With their competitors rolling out both voice and WAP access to services, MyRubberBands.com has no choice but to follow suit or lose market share in the cutthroat world of elastic band marketing. Due to market pressures, the new system must be up and running as soon as possible, and given this short development cycle, the requirements have been scaled back to providing simply voice and WAP access to a customer's order status data.

However, some thought can still be given to the future. Rather than develop a quick and dirty "throwaway" voice interface, by putting in a little extra work now, the engineers can build a reusable infrastructure. By exporting their database to an XML format, they access the power of XSL to create VoiceXML and WML interfaces, and are able to transparently replace parts of the existing HTML site with dynamically created pages.

System Architecture

The figure on the next page is a block diagram showing the existing components of the system, and the relationships to the new XML/XSLT system required to implement the voice interface.

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This article was originally published on January 1, 2002

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