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