Fuzzy boundaries are defined as the area boundaries arising from the way space is structured internally and how this relates to the external structure of space, and so maintaining inter-accessibility between the areas.
Yang, T. & Hillier, B. (2007), The fuzzy boundary: the spatial definition of urban areas, In: the Proceedings of 6th International Space Syntax Symposium, 091-16. pp.091-02;
Hillier, B. (2009),Spatial sustainability in cities: organic patterns and sustainable forms. In: Koch, D. and Marcus, L. and Steen, J., (eds.) Proceedings of the 7th International Space Syntax Symposium. (pp. p. 1). Royal Institute of Technology (KTH): Stockholm, Sweden, k01.1-20. K01:3