HUMAN-PERFORMANCE ANALYSIS AND ENGINEERING GUIDELINES FOR DESIGNING GRAPHICAL NETWORK MANAGEMENT INTERFACES

This study clarifies the effects of network complexity and network map transformation on the ability of network managers to use graphic netw ork displays. Maps of Japan and the United States with outlines of the ir respective prefectures or states were displayed on a CRT. Each map displayed a fictitious network of nodes and their interconnections. Th ese networks were two-level hierarchical and non-meshed, meaning that each low-level node was connected to a single high-level node. but not all high-level nodes were linked together. The subjects' task was to identify a path between two low-level nodes. In each trial, two low-le vel nodes were highlighted, and the subject attempted to find the shor test path between these nodes. This was done by using a mouse to selec t intermediate nodes. Completing a path required a minimum of 4 node t raversals. Three variables were manipulated. First, the number of node s was defined as the total number of low-level nodes in a network (70, 150, or 200). The second variable was the level of transformation. Ve ry densely populated areas of the maps were systematically transformed to reduce congestion. There were three levels of transformation. The final variable was the country map used, that is, the map of Japan and the map of the United States. Several behavioral measures were used. The most informative appeared to be the rime required to complete a pa th (the response time), and how often subjects returned to previous po rtions of a path (back-ups). For both of these measures, the data patt ern was essentially the same. Increasing the number of nodes hurts per formance. This was particularly pronounced when the map of Japan was t ested. However, as the level of transformation increased, this effect was substantially reduced or completely eliminated. The results are di scussed in terms of engineering rules and guidelines For designing gra phical network representations.