1. A method of identifying at least one solid model having a predetermined similarity to a query model in a knowledge-base storing a plurality of solid models, the method comprising the steps of: comparing an undirected model dependency graph of the query model constructed from a set of features including one or more manufacturing features selected from the group consisting of a shape, a topology, a form, features of a manufacturing process, assembly/mating features, interactions between features which influence process plans and selection of machining operations, and fixtures and feature space of manufacturing operations, with an undirected model dependency graph of at least one of the plurality of solid models constructed from a set of features including one or more manufacturing features selected from the group consisting of a shape, a topology, a form, features of manufacturing process, assembly/mating features, interactions between features which influence process plans and selection of machining operations, and fixtures and feature space of manufacturing operations, to test for the existence of a subgraph isomorphism between the undirected model dependency graphs of the query model and the at least one of the plurality of solid models using Ullmann's algorithm for subgraph isomorphism with a matrix employed by the Ullmann's algorithm being initialized based on an n-region density of nodes in the matrix; if at least one subgraph isomorphism is found in said comparing step, identifying at least one solid model having the subgraph isomorphism; and if no subgraph isomorphism is found in said comparing step, identifying a one model having a large enough common subgraph of the undirected model dependency graph.