Abstract: A document search system comprises an ontology editor including a graphical user interface for creating and modifying a hierarchical query data structure (ontology) containing a plurality of search terms (concepts), a scanner scanning a communication network and providing a scan list, an ontology indexer matching the documents stored in the scan list with the search terms contained in the query data structure (ontology) and indexing the documents dependent on the occurrence of one or more of the search terms in the document, and a display unit for displaying the indexed documents in a hierarchical order. It further comprises a graphical user interface for selecting search terms from the query data structure (ontology); thus formulating a query, and another one for displaying graphical representations of results of the search and for controlling the graphical representations. And it further comprises a user interface for selecting one or more document sets (e.g.