DefinePK

Abstract

In this study, we extend XML Schema with nonmonotonic inheritance due to its powerful modeling ability to support multiple inheritance, overriding of elements or attributes inherited from super-elements, blocking of the inheritance of elements or attributes from super-elements and conflict handling. Another key feature of object-oriented data models is polymorphism. We introduce it into XML Schema to support polymorphic elements and polymorphic references. Moreover, we define a formalization to represent these features and present some validation rules to validate whether an XML instance document conforms to an Extended XML Schema based on the formalization. Finally, we extend XQuery to support the polymorphic feature.