INGRID: A graph invariant manipulator (Q1113914)

INGRID, a software system for assisting researchers and students of graph theory, is described. It is a partial commentative rule-based system using forward chaining, consists of approximately 1200 production rules, and is written in Berkeley Pascal on a VAX 11/780 under UNIX. INGRID has a data base of 36 graphical invariants and approximately 350 theorems symbolically relating these invariants. A set of one or more user- supplied restrictions upon the values of some invariants is propagated by INGRID, via the theorems, into intervals of possible values for other of the invariants. With the simple user interface provided by INGRID, even a graph theory novice can often discern properties of a graph that might normally require the capabilities of a well-informed expert.