Some embodiments of the invention provide a method for identifying a path
between a set of source states and a set of target states in a space with
more than two dimensions. In some embodiments, the space includes a set
of states and a transition map that specifies a set of states that can be
reached from each particular state. At least some of the states are
non-zero dimensional states. For instance, in some embodiments, the space
is a graph that includes points, lines, and surfaces. The method
specifies at least one path that starts from one state. It then
iteratively specifies new paths by expanding previously specified paths
to other states in the space until identifying a path that connects the
source and target states. At least one of the expansions of a previously
specified path includes an expansion in more than two dimensions of the
space.