July/August 2005

By James A. Larson

Many Web developers use XML to represent data and a transformation language, such as XSLT, ASP, or ColdFusion, to transform the XML data to an HTML user interface.  Developers change the values of the XML data without having to manually recode the HTML user interface.

Figure 1. Using a Transformation Processor to

generate multiple user interfaces

Transformation languages can also convert XML data into different user interfaces for access by users with different devices.  As illustrated in Figure 1, developers can use a transformation language to extract and reformat XML data to HTML for publishing on the Web, to Word or PDF for printing, to VoiceXML 2.0 for telephone access, and to a combination of HTML, and either SALT or X+V for multimodal access. 

Suppose a user needs to specify the color of a T-shirt that he or she is ordering.  The developer specifies the color options, instructions for choosing the color, and other explanations once in the XML schema.  The transformation processor then extracts the information and automatically inserts it into each verbal, visual, and multimodal user interface.  Figure 2

Figure 2. Simplified schema containing meta information about the color element

http://www.w3.org/2001/XMLSchema">                                              Color                Which color? for example, blue.                                  We need the color to manufacture the right T-shirt for you

illustrates a simplified XML schema illustrating metadata about the item in an items-for-sale XML file.  Figure 3 summarizes how this metadata can be used in a visual HTML and a verbal VoiceXML user interface.  If you are interested in additional details about this example, see http://www.larson-tech.com/.

Specifying meta information and using mapping languages to construct each user interface has the following advantages: 

• Consistent input options.  The user always selects from the same input options. The verbal grammar has the same options as the visual pull-down menu.
• Consistent help instructions.  The verbal instructions and help messages are consistent with the visual labels and alert messages.

By specifying user input options and instructions once and transforming those options and instructions for each user interface, developers minimize manual changes to the user interface and provide consistent user instructions, options, and help messages across multiple user interfaces.