Gilberto Câmara Antônio Miguel Vieira Monteiro João Argemiro Carvalho Paiva Jonas Gomes Luiz Velho Towards a unified framework for spatial data models. 17-25 2000 7 J. Braz. Comp. Soc. 1 db/journals/jbcs/jbcs7.html#CamaraMPGV00