The WebWorks ePublisher engine uses XML, XSL, and XPath as the foundation for all processing. While extremely powerful, XSL has many shortcomings when used to perform system level scripting tasks. Operations such as working with files and advanced string operations are not included in the standard XSL language.

XSL does provide a generic extension mechanism to add new features to the base language. WebWorks ePublisher provides a standard set of extension objects which enable XSL to generate all required formats.