Analogies can generally be expressed as maps from important
features of a source to the corresponding important features of
a target.

Analogies appear frequently in everyday language.  Within
vehicle reasoning, reasoning in the target space, has advantages
over within tenor reasoning, the source space.  The reasoning
may use portions of the target space that do not correspond to
any portion of the source space.

Prodigy is a tool for generating a plan from similar previously
used planes by case based reasoning and analogy.

Prodigy has been used to generate driving routes in Pittsburgh
from previous driving routs.  The program brings up previous
relevant driving routs and connects portions of these old routs
with novel routs.  The program is more efficient than programs,
which generate entirely novel routs because of the use of
previously generated solutions.  Additionally, the program can
learn to adjust to changing traffic conditions based on time of
day or weather or other variables.

Analogies can be generated in concept graphs, where each object
is a node and each relationship is an edge, by finding portions
of the source graph, which have the same structure as portions
of the target graph.

ACT R generates analogy maps from relationships.  This is
similar to concept graphs except that the arguments of a
relationship can be a relationship and there can be more than
two arguments.  Additionally each argument in a relationship has
a role.  The map is generated by first choosing an element in
the source and finding a corresponding element in the target,
then choosing one of the roles of the source element and finding
a corresponding role for the target element.  The relationship
in the source and target which has this element in this role
becomes the new element in the source and target.  A new role is
chosen and the cycle continues until a previously mapped
relationship is reached or a relationship that has no role in
another relationship is reached.  The way corresponding roles
are found in the target is dependent on how recently and how
many times the potential target role has been used and the
conceptual distance between the source and potential target.