ToX - The Toronto XML Engine
The authors present ToX - the Toronto XML Engine - a repository for XML data and metadata, which supports real and virtual XML documents. Real documents are stored as files or mapped into relational or object databases, depending on their structuredness; indices are defined according to the storage method used. Virtual documents can be remote documents, defined as arbitrary WebOQL queries, or views, defined as queries over documents registered in the system. The system catalog contains metadata for the documents, especially their schemata, used for query processing and optimization.