17. The computer storage medium of claim 15 , wherein the hierarchical model is defined to comprise: a model table configured to comprise one or more attributes of the hierarchical model; a Node_Class table configured to comprise information related to types of nodes in the hierarchical model; and a Node table configured to comprise the definition of each node within the hierarchical model and corresponding hierarchy information.
17. The computer storage medium of claim 15 , wherein the hierarchical model is defined to comprise: a model table configured to comprise one or more attributes of the hierarchical model; a Node_Class table configured to comprise information related to types of nodes in the hierarchical model; and a Node table configured to comprise the definition of each node within the hierarchical model and corresponding hierarchy information. 18. The computer storage medium of claim 17 , wherein the model table, the Node_Class table and the Node table are linked to each other by a plurality of strong links which make use of the Row-ID of the respective table, each strong link defining one or more dependencies of data in a first set of one or more tables to data in a second set of one or more tables, each strong link defining the underlying structure of the hierarchical model.