Metric Details for Natural-Language Spatial Relations
Max Egenhofer and A. Rashid Shariff ACM Transactions on Information Systems 16 (4): 295-321, 1998.
Abstract
Spatial relations often are desired answers that a geographic
information system (GIS) should generate in response to a
userÕs query. Current GISs provide only rudimentary support
for processing and interpreting natural-language-like spatial
relations, because their models and representations are primarily
quantitative, while natural-language spatial relations are usually
dominated by qualitative properties. Studies of the use of spatial
relations in natural language showed that topology accounts for a
significant portion of the geometric properties. This paper
develops a formal model that captures metric details for the
description of natural-language spatial relations. The metric
details are expressed as refinements of the categories identified
by the 9-intersection, a model for topological spatial relations,
and provide a more precise measure than does topology alone as to
whether a geometric configuration matches with a spatial term or
not. Similarly, these measures help in identifying the spatial term
that describes a particular configuration. Two groups of metric
details are derived: splitting ratios as the normalized
values of lengths and areas of intersections; and closeness
measures as the normalized distances between disjoint object
parts. The resulting model of topological and metric properties was
calibrated for sixty-four spatial terms in English, providing
values for the best fit as well as value ranges for the significant
parameters of each term. Three examples demonstrate how the
framework and its calibrated values are used to determine the best
spatial term for a relationship between two geometric objects.
Full article
Max Egenhofer and 
A. Rashid Shariff
