A hierarchical category model for geometrical product specifications (GPS)

International standards for tolerancing (ISO GPS) have undergone considerable evolutionary changes to meet the demands of the modern information age. Their expanding quantity and complexity have proposed a great obstacle to their informatisation progress. In this paper, a solution to reduce the complexity is coarse-graining the GPS knowledge into five hierarchy levels. A high-level abstraction mathematical theory - category theory is employed to model the GPS hierarchy, in which structures are modelled by categorical concepts such as categories, morphisms, pullbacks, functors and adjoint functors. As category theory is hierarchically structured itself, it can prove that the multi-level GPS framework is constructed in a rigorous manner and is expected to facilitate the future autonomous integration between design and measurement in the manufacturing system.