Efficient XQuery Support for Stand-Off Annotation

XML annotations are a widely occurring phenomenon in many application fields, and XML databases should be used to store and query such data. To provide intuitive and fast querying of annotations, we make a case for extending XPath with four new axis steps, that correspond with socalled StandOff joins, introduced here. The new steps can be efficiently implemented using a region index and fast looplifted StandOff MergeJoin algorithms. These techniques were added to the open-source XML DBMS MonetDB/XQuery, and we show in our evaluation it thus becomes capable of interactively querying >GB annotation databases.