db/conf/gis/RazaK99.html Ale Raza Wolfgang Kainz Cell Tuple Based Spatio-Temporal Data Model: An Object Oriented Approach. 20-25 GIS1999/P020.pdf 1999 conf/gis/99 ACM-GIS http://doi.acm.org/10.1145/320134.320140 db/conf/gis/gis99.html#RazaK99