1. A method for traversing between a higher level net occurrence and a lower level net occurrence in a hierarchical model of a system design, wherein the model includes a first cell that describes a first device within the system and a second cell that describes a second device within the system, wherein the higher level net occurrence is associated with the first cell and the lower level net occurrence is associated with the second cell and the first cell is at least one level higher in the model than the second cell, the method comprising: defining a current net occurrence, which is one of the higher level net occurrence and the lower level net occurrence; retrieving a first describer pointer for the current net occurrence, wherein the first describer pointer points to a model object that is used to describe the current net occurrence; retrieving a first owner pointer for the current net occurrence, wherein the owner pointer points to the owner cell of the current net occurrence; and using the current net model object of the current net and owner cell to traverse the hierarchical model.