db/conf/gis/BorgesLD99.html Karla A. V. Borges Alberto H. F. Laender Clodoveu A. Davis Spatial Data Integrity Constraints in Object Oriented Geographic Data Modeling. 1-6 GIS1999/P001.pdf 1999 conf/gis/99 ACM-GIS http://doi.acm.org/10.1145/320134.320136 db/conf/gis/gis99.html#BorgesLD99