Methods for product data management and corresponding systems and computer-readable mediums. A method includes receiving a three-dimensional CAD model in the data processing system, the CAD model including a plurality of geometries. The method includes receiving at least one system-found equivalence class (EC) including at least one of the geometries, the system-found EC being of a specified EC type, and receiving at least one persistent EC of the specified EC type including at least one of the geometries. The method includes completing any unique persistent member of the persistent EC by finding any other geometries in the CAD model that have an EC relationship with the unique persistent member of the specified EC type. The method includes expanding the user-defined persistent EC by adding any unique found members of the specified EC type to produce a combined EC, and storing and reusing the combined EC.