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Modular speech application development using VoiceXML; reusability and modularity are key components for VoiceXML adoption. (voice xml).

Article Excerpt
One thing weve learned from Web-based application development is that tools are useful only if they can reuse components and third-party libraries and make it easy to assemble applications. This article reviews how we can build modular speech applications using VoiceXML. The focus will be on the language constructs that VoiceXML provides for modularization and reusability and on vendor-specific approaches toward creation of a library of reusable dialogs for speech applications.

As a language, VoiceXML is designed for reusability and modularity. Similar to the Web paradigm, VoiceXML supports modularization of the application components through document-to-document navigation (through menus, form submits, subdialogs etc.). The "src" attribute associated with a number of VoiceXML elements allows URL-based loosely coupled integration.

Since we're used to a hyperlinked world today, we take this for granted, but if we compare it with speech applications developed earlier, it's really like comparing a huge compiled application with a loosely coupled yet integrated application. We're used to separating Web application functionality into multiple sets of scripts (Perl scripts, PHP pages, ASP.NET pages, JavaServer Pages), images, and other media. This capability has been leveraged by VoiceXML as the language supports division of applications into VoiceXML documents (which can be dynamically generated through server-side programming), grammars, prompts, and subdialogs.

However, we'd be kidding ourselves if we didn't acknowledge that development of rich, high-quality speech applications is complex. VoiceXML does make it really simple to assemble a speech application, but we still need to create complex grammars and dialogs that can handle the complex conversations that the application needs to support.

This is where we can utilize the skills available within the speech recognition industry in the form of dialog and grammar experts. And this is where reusable components come to the rescue. Reusable components represent best practices and frequently used dialogs/ grammars that can be used by an application developer (or, rather, an assembler) to create a high-quality speech application.

For instance, if we were to develop a stock-trading application, we'd need the ability to recognize the various companies traded on the stock exchange. If application developers were to include this capability as part of...

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