Reference tessellation footprint graphwe focus direct neighborhoods

82 5 Spatial Representation and Reasoning

Footprints

These shortcomings lead to a new type of footprint based on a pSRT as defined in section 5.2.1. Figure 5.5 gives an example. In the following, this footprint is used. The polygons in the plane will also be referred to as reference units. Place names are extensionalized in terms of reference units which simply means that there exists a binary relation between a place name and a reference unit.

In a homogeneous decomposition by tessellation two kinds of structure with spatial character interact. Firstly, there is the recursive structure of the decomposition reflected by the decomposition tree. Secondly, there exists a neighborhood structure due to fact that a polygon shares each of its edges or each of its vertices with at most one other polygon.

Fig. 5.5. Reference tessellation footprint.

Neighborhood Graph

If there is no interesting information items linked to a polygonal footprint, a good place to search for further information are its neighboring polygons. Alternatively, one could search in those polygons that are part of the same de-composition. Obviously, this leads to two different criteria of spatial relevance, which will be discuss later. In other words, a spatial relevance metric can be based on either the decomposition tree or the neighborhood graph (fig. 5.6). [99] discussed the issues about inferring relevance from spatial neighborhood and concluded that known approaches based on neighborhood graphs such as the RCC calculus are not sufficient enough to provide satisfactory results if using planar polygons as a basic model.