While graphs are normally defined in terms of the 2-place relation of
adjacency, we take the 3-place relation of interception as the basic p
rimitive of their definition. The paper views graphs as an economical
scheme for encoding interception relations, and establishes an axiomat
ic characterization of relations that lend themselves to representatio
n in terms of graph interception, thus providing a new characterizatio
n of graphs. (C) 1996 John Wiley & Sons, Inc.