1. Department of Architecture, Rhode Island School of Design, Providence, RI 02903, USA
2. Center for Spatial Information Science, The University of Tokyo, Tokyo 277-0882, Japan
3. Department of Computer Science, The University of Bath, Bath BA2 7AY, UK
4. Department of Urban Planning and Design: 8/F, Knowles Building, The University of Hong Kong, Pokfulam Road, Hong Kong