EquiX Easy Querying in XML Databases

EquiX is a powerful, yet easy to use query language for XML. Knowledge of XML syntax is not required in order to use EquiX. Yet, EquiX is able to express rather complicated queries. For example, it can express quantication, negation and aggregation. The main goal in designing EquiX is to strike the right balance between expressive power and simplicity. EquiX has a form-based GUI that is constructed automatically from the DTD of XML documents. Query forms are built from well known HTML primitives. The result of a query in EquiX is a collection of XML pages, and it is automatically generated from the query without explicit specication of the format of the result. The DTD describing the result documents is derived automatically from the query form and the original DTD. An algorithm for query evaluation that runs in polynomial time, even when the query is considered as part of the input (i.e., combined complexity), is given for a large class of Equix queries, i.e., queries without internode constraints.