Wenzhong Shi Bisheng Yang Qingquan Li An object-oriented data model for complex objects in three-dimensional geographical information systems. 411-430 2003 17 International Journal of Geographical Information Science 5 http://taylorandfrancis.metapress.com/openurl.asp?genre=article&issn=1365-8816&volume=17&issue=5&spage=411 db/journals/gis/gis17.html#ShiYL03