Understanding spatial structure from network data : theoretical considerations and applications

In the past decade, analysis of flow data has been of practical concern in most studies dealing with regionalization and transportation land-use problems. Existing methodologies however show difficulties to cope with the increasing complexity of spatial structures because of the 'variety' of roles which nodes and links are likely to play within the overall interaction structure. By applying graph-theoretic considerations, it is argued that an investigation of both direction and versus of network links can reveal a whole range of spatial 'typologies' . The first section provides some arguments for a deeper understanding of flow data. It is shown that a conceptualisation of network flows as a result of interacting places defines a general framework according to which a whole range of interaction patterns (e.g. spatial structures) can be recognised. Two empirical applications of these ideas are described in the following sections. Section 3 presents an extension of the dominant-flow approach which is applied to the journey-to-work flows for the Piedmont region over the last three decades. Besides identifying the hierarchical structure, the consideration of the sub-dominant and complementary flows allows to identify a typology of relationships and get a deeper insight in the changes of the regional spatial structure during the 1971-1991 period. In section 4, an analysis of the residential mobility for the Turin metropolitan area is carried out. By analysing the sub-set of links which have a 'strict complementarity', some 'circuit-like-structures' are revealed which may be also interpreted as interlinked residential market areas