Described is a method and data structure that enables an object to be specified declaratively within a markup document. The markup document may be XML-based. In accordance with the invention, the object is written based on a mapping. The mapping includes a URL attribute for defining a location for a definition file having assemblies and namespaces where classes are specified. The class name is mapped to the markup document as a tag name. Properties and events of a class are mapped to attributes of the tag associated with the class. The method further includes a method to parse the markup language to create a hierarchy of objects. Attributes that do not map directly to a class are defined with a definition tag. The definition tag is also used to add programming code to a page.