The Essence of XML (Preliminary Version)

The World-Wide Web Consortium (W3C) promotes XML and related standards, includingXM L Schema, XQuery, and XPath. This paper describes a formalization XML Schema. A formal semantics based on these ideas is part of the official XQuery and XPath specification, one of the first uses of formal methods by a standards body. XML Schema features both named and structural types, with structure based on tree grammars. While structural types and matching have been studied in other work (notably XDuce, Relax NG, and previous formalizations of XML Schema), this is the first work to study the relation between named types and structural types, and the relation between matchinga nd validation.