ERX: a data model for collections of XML documents

XML (eXtensible Mark-up Language) is able to represent any kind of structured or semi-structured document, such as papers, Web pages, database schemas and instances, style sheets, etc. However, the tree structure of XML documents, induced by mark-up nesting, does not provide a sufficiently expressive and general conceptual model of data in the documents, particularly when multiple source documents are processed at the same time. This paper proposes the ERX (Entity Relationship for XML) data model, an evolution of the entity-relationship model that copes with the peculiar features of XML. ERX is devised to provide effective support for the development of complex XML processors for advanced applications.