The act of creating and building up a BIM model's geometry and data inside an authoring tool like Revit, as opposed to coordinating, reviewing, or federating models made elsewhere. Revit, ArchiCAD, and Tekla Structures are authoring tools; Navisworks and Solibri are not - they federate and review what authoring tools already built. Knowing which category a piece of software falls into explains why a clash report from Navisworks still has to be fixed back in the authoring model, not in Navisworks itself.