A Comparative Analysis of XML Schema Languages

Abstract

XML (Extensible markup language) is playing progressively more important role in the exchange of wide variety of data on the Web and in many other applications. XML is not only used for data exchange, but also has it changed the concept of data formats, and that is the reason why it has become a standard and powerful data structure on the Internet. XML has simple syntax and can thus compose well-formed documents by following simple rules. To represent and validate these data structures and to check a well formed XML document, several validation languages are used. These validation languages are known as Schema languages. This paper presents a comparative analysis of four schema languages focusing on how these four languages are used, what data types are used in them, and how they are syntactically different from one another. The languages discussed in this paper are: DTD, XML Schema, RelaxNG, and DSD2. The benefit of the comparative analysis is to give the basic knowledge about two newly introduced schema languages (DSD2 and RelaxNG) against well-known and widely used languages (DTD and XML Schema). This comparison gives some basic knowledge about selected schema languages, illustrates the difference in their syntax, and demonstrates where to use which schema language.