1. One or more computer devices for maintaining a hierarchical conceptual framework corresponding to a physical three-dimensional site, comprising: a first storage component to store environment information, where the environment information includes information regarding a number of environment levels relating to the physical three-dimensional site and information regarding hierarchical relationships associated with the site levels; a second storage component to store item information, where the item information includes information regarding a number of items for placement in the site levels and information regarding hierarchical relationships associated with the number of items; a third storage component to store information regarding a spatial relationship of one or more items from the number of items within the number of site levels; a processor to determine, responsive to selection of one or more of the number of items for placement within one or more of the number of the site levels, whether each one of a plurality of hierarchical item configurations is valid; and a fourth storage component to store a modeled physical environment including those of the hierarchical item configurations that are valid.