A computer-readable storage medium having a data structure for representing a plurality of objects. The data structure includes a first data field storing data associated with a taxonomy type. The data structure also includes a second data field storing data associated with a reference to a model instance of an object classified by the taxonomy type. The model instance identifies an entity represented by the classified object. A third data field stores a first data set having data stored in the second data field. The first data set identifies a set of one or more objects related to the classified object positioned higher in a hierarchical structure than the classified object. A fourth data field stores a second data set having data stored in the second data field. The second data set identifies a set of one or more objects related to the classified object positioned lower than classified object.