EReX: A Conceptual Model for XML

In the last few years, XML has been widely used as a logical data model, and several database applications are modeled in XML. To model a database application in XML, we should first come up with a conceptual design for representing the application requirements, and then translate this conceptual design to XML. Existing conceptual models like the ER (Entity Relationship) model, UML and ORM do not have modeling capabilities to represent main features provided by XML, such as union types. In this work, we extend the ER model with additional features; we call our conceptual model as EReX (ER extended for XML). Translating an EReX design to XML enables us to make use of the different features provided by XML. Our approach further enables us to study a fundamental problem facing XML database community today: what structural and constraint specification should be provided in XML so that any generic database application can be modeled in XML.