From shape to threat: exploiting the convergence between visual and conceptual organization for weapon identification and threat assessment

The present work is a part of a larger project on recognizing and identifying weapons from a single image and assessing threats in public places. Methods of populating the weapon ontology have been shown. A clustering-based approach of constructing visual hierarchies on the base of extracted geometric features of weapons has been proposed. The convergence of a sequence of visual hierarchy trees to a conceptual hierarchy tree has been discussed. For illustrative purposes, from the growing conceptual ontology, a conceptual hierarchy tree has been chosen as a point of convergence for a sequence of visual hierarchy trees. A new approach is defined, on the base of the Gonzalez' algorithm, to generate the visual hierarchies. The closest visual hierarchy tree is selected as the search environment for a query weapon. A method of threat assessment is proposed. This method uses the attribute-rich conceptual hierarchy tree to evaluate the results from the visual hierarchy tree search. The two trees are linked at the leaf-level, because the visual hierarchy closest to the conceptual has the same distribution of the leaf nodes. A set of experimental results are reported to validate the theoretical concepts. A portion of the existing weapon ontology is used for this purpose.