DTD schema: a simple but powerful XML schema language

Abstract

PurposeThe purpose of this paper is to describe a novel XML schema language called DTD Schema that solves major limitations of document type definition (DTD) and supports features that XML Schema supports in a simple and concise way.Design/methodology/approachDTD Schema is designed based on DTD and data definition language of object‐oriented and object‐relational databases. It extends DTD with namespaces, richer built‐in types and user‐defined subtypes, local elements and attributes, complex types with nonmonotonic multiple element and attribute inheritance with overriding, blocking, conflict handling, and polymorphism.FindingsXML Schema is recommended by W3C as the schema language for XML. It uses a set of predefined XML tags to define the schema, which is often a long, intricate specification, full of details and concepts and its verbose syntax often doubles or triples the document length. It is so complicated that even XML experts do not find it human‐readable, mostly due to the XML‐based syntax.Research limitations/implicationsThe only limitation is that DTD Schema is not in XML. But for the same reason, it is simple and concise.Practical implicationsDTD schema is halfway between DTD and XML Schema and thus it is less complex and much easier for human to use than XML Schema.Originality/valueDTD Schema supports all functionalities of XML Schema and also the best of object‐oriented features including multiple inheritance, overriding, blocking, conflict handling and polymorphism. Therefore, it is much more expressive than XML Schema.