Conceptual Modeling of XML Schemas

XML has become the standard format for representing structured and semi-structured data on the Web. To describe the structure and content of XML data, several XML schema languages have been proposed. Although being very useful for validating XML documents, an XML schema is not suitable for tasks requiring knowledge about the semantics of the represented data. For such tasks it is better to use a conceptual schema. This paper presents an extension of the Entity Relationship (ER) model, called X-Entity, for conceptual modeling of XML schemas. We also present the process of converting a schema, defined in the XML Schema language, to an X-Entity schema. The conversion process is based on a set of rules that consider element declarations and type definitions and generates the corresponding conceptual elements. Such representation provides a cleaner description for XML schemas by focusing only on semantically relevant concepts. The X-Entity model has been used in the context of a Web data integration system with the goal of providing a concise and semantic description for local schemas defined in XML Schema.