http://doi.acm.org/10.1145/262762.262765 db/journals/sigmod/ClementLGMK97.html Gilles Clement Christian Larouche Denis Gouin Paul Morin Henry Kucera OGDI: Toward Interoperability among Geospatial Databases. 18-23 sigmodR/26-3/P018.pdf 1997 26 SIGMOD Record 3 db/journals/sigmod/sigmod26.html#ClementLGMK97 http://www.acm.org/sigmod/record/issues/9709/ODGI.ps