The World Wide Web provides the means for theintegration of clinical computer systems. Extensible Markup Language (XML) and Extensible Stylesheet Language (XSL) are newly developed and standardized Internet protocols. Development of custom data entry forms requires significant programming resources in clinical information system development and management. Visual design tools and a modifiable, template-driven approach may facilitate this process. However, these approaches generally require the predefinition of data form element types. This paper describes an XML/XSL-based technology enabling post hoc definition of elementary and composite data entry form element types.