Yu Tang Luo Chen Ning Jing Towards System Architecture of Spatial Information Grid and Service-Based Collaboration. 127-138 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3289&spage=127 2004 conf/er/2004w ER (Workshops) db/conf/er/erw2004.html#TangCJ04