InformationWeek
Defining The Business Value Of Technology
June 28, 1999
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Through the use of an XSL style sheet, an XML document can be transformed into the code or commands necessary for the particular channel. For the Web application, a style sheet can be written to transform the XML document into HTML. This is a fairly typical use of XSL. However, there's no reason to stop there. Additional style sheets can be created to operate on the same XML document, but instead of producing HTML, they could produce IVR scripts or a bank teller interface.
Consider this real-world example: KPMG is building a Voluntary Benefits Enrollment system for a major insurance company. The requirements are to support a variety of insurance products via paper forms typed in to administrator screens, a call center, a business partner extranet, and finally the Internet.
"Our mandate is to create a set of services delivered via one application platform that can be accessed through all these different channels," says senior manager Richard Walker, who is leading the development effort. "We've chosen XML for all our data so that we can represent the data contained in a benefits enrollment application totally independent of its visual representation. Through the creative use of style sheets, we will then make that data available to each channel in an appropriate presentation style."
Personalize The Experience
Employing such a mechanism doesn't only serve to create the different delivery channels, but can also be used to personalize those channels. Say I want to show high net-worth customers more account data than my regular customers. Instead of changing and recompiling code now and undoing that code change when I decide to offer this data to all customers, I could just write a new style sheet that acts upon the XML document that contains all the data and presents it to two sets of customers in a different manner.
This type of mechanism is quite compelling, in that it allows presentation-specific changes to business logic to be rendered in almost real time.
Build Around XML
XML can also be used to address the limitations inherent in the proprietary nature of a UML model mentioned earlier. It's possible to start with a UML model and express it instead using XML, an open standard.
Again, just to clarify, UML isn't proprietary--it's an open standard under the auspices of the OMG. It's the way a UML model is stored that's proprietary or, to be more precise, vendor dependent.
Expressing and storing a UML model in XML creates many interesting possibilities. The XML model could be decorated in a structured manner with additional attributes that UML may not support. Also, having the model in XML again allows XSL to be utilized. The style sheet in XSL is somewhat misleading. Style sheet languages such as the Cascading Style Sheet standard used in Web development are typically used for defining and creating presentation--the user interface. XSL can be used for this as well. I can take the XML representation of my object model and automatically generate the user-interface tier, such as HTML forms.
XSL should be thought of as less of a styling mechanism and more of a transformation engine. Creating HTML from XML is just one example of a transformation. XSL can also be used to transform an XML document into pretty much any representation. Once you have your business model expressed in XML, you will begin to think of many such representations.
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