Spatial Relations, Qualitative

Geographical information systems (GIS) typically contain many gigabytes of quantitative spatial data; a major problem is how to best query and abstract this data for presentation to the human user. One possibility is through the use of maps and other graphical interfaces. The other, explored here, is through sets of qualitative spatial relations, such as the topological ones that have found their way into the ISO 19107 Spatial Schema standard. Such relations may be used to specify a wide variety of spatial information, including topological relationships, orientation, size, distance, location, and certain aspects of shape.

Representing space has a rich history in the physical sciences and serves to locate objects in a quantitative framework. At the other extreme, spatial expressions in natural languages tend to operate on a loose partitioning of the domain. Representation for this less precise description of space proliferated more or less on an ad hoc basis until the emergence of qualitative spatial reasoning (QSR); thereafter, the partitioning was done more systematically. This entry briefly outlines the major issues and aspects of qualitative spatial relations, concentrating on aspects most relevant to GIS.

There are many different aspects to space and therefore to its representation. Not only do we have to decide on what kind of spatial entity we will admit (i.e., commit to a particular ontology of space), but we also can consider developing different kinds of ways of describing the relationship between these kinds of spatial entities; for example, we may consider just their topology, their sizes or the distance between them, their relative orientation, or their shape. The following sections give an overview the principal techniques that have emerged to represent these different aspects of qualitative spatial knowledge.