US Patent 7853940 Creating a reference using tracking data

Creating a reference to data used to construct a computer-aided design model includes storing model data with tracking data, where the tracking data identifies the model data. A reference is created and the tracking data is associated with the reference to enable the reference to refer to the model data. A modeling operation is executed, which retrieves the tracking data associated with the reference, traverses a data structure defining the computer-aided design model while attempting to match the tracking data associated with the reference to the tracking data stored with the model data, and returns geometric data stored in the model data.