Tree patterns with Full Text Search
Tree patterns with full text search form the core of both XQuery Full Text and the NEXI query language. On such queries, users expect a relevance-ranked list of XML elements as an answer. But this requirement may lead to undesirable behavior of XML retrieval systems: two queries which are intuitively (e.g., without ranking) equivalent return differently ordered lists of elements. We show that the best performing XML retrieval semantics has this behavior. We also show how minimization of tree patterns can efficiently solve this problem.