title: qursed : querying and reporting semistructured data. authors: yannis papakonstantinou , michalis petropoulos , vasilis vassalos. venue: sigmod conference. year: 2002
title: constraints for semistructured data and xml. authors: peter buneman , wenfei fan , j &#233; r &#244; me sim &#233; on , scott weinstein. venue: acm sigmod record. year: 2001