1. A method of indexing structured documents, the method comprising the steps of: parsing at least one schema of the structured documents to determine predefined deteministic relationships between components of the structured documents to be indexed; removing from one or more sets of indices those components whose occurrences can be deduced by virtue of said determined predefined deterministic relationships from occurrences of another indexing component to provide corresponding one or more smaller sets of indices; and indexing said structured documents in accordance with said one or more smaller sets of indices.