title: cost estimation of user-defined methods in object-relational database systems 1999. authors: kinji ono , jihad boulos. venue: sigmod record. year: nan
title: vxmlr : a visual xml-relational database system 2001. authors: aoying zhou , hongjun lu , shihui zheng , yuqi liang , long zhang , wenyun ji , zengping tian. venue: very large data bases. year: nan