1. A computer readable medium storing instructions for causing a computer to display a portion of a schematic representation of a scene, performing the steps of: generating a list of relationships, each entry in the list of relationships identifying two elements and a link defining a relationship type between the two elements; receiving selection data input specifying one relationship type of a plurality of relationship types; and displaying the portion of the schematic representation of the scene including any nodes and any links in the list of relationships related by the one relationship type specified by the selection data.