1. A method for obtaining a model of data describing a physical structure, the method comprising: defining a three-dimensional (3D) object that corresponds to a physical structure, the 3D object comprising a set of topological elements that each has an initial geometric definition; and creating a subsequent model of the data by updating a subset of the topological elements in the 3D object, each updated element in the subset having a geometric definition that has changed relative to its initial geometric definition.