prefer to view part or all of the network at varying levels of detail. Hierarchical clustering provides a framework for viewing the network at different levels of detail by superimposing a hierarchy on it. Nodes are grouped into clusters, and clusters are themselves placed into other clusters. Users can then navigate these clusters until an appropriate level of detail is reached. This article describes an experiment comparing two methods for viewing hierarchically clustered networks. Traditional full-zoom techniques provide details of only the current level of the hierarchy. In contrast, fisheye views, generated by the "variable-zoom" algorithm described in this article, provide information about higher levels as well. Subjects using both viewing methods were given problem-solving tasks requiring them to navigate a network, in this case, a simulated telephone system, and to reroute links in it. Results suggest that the greater context provided by fisheye views significantly improved user performance. Users were quicker to complete their task and made fewer unnecessary navigational steps through the hierarchy. This validation of fisheye views is important for designers of interfaces to complicated monitoring systems, such as control rooms for supervisory control and data acquisition systems, where efficient human performance is often critical. However, control room operators remained concerned about the size and visibility tradeoffs between the fine detail provided by full-zoom techniques and the global context supplied by fisheye views. Specific interface features are required to reconcile the differences.

Even when companies improve their performance, they often have difficulty achieving real competitive advantage. In the face of often astounding operational improvements, most customers just don't seem very excited. The reason? Customers have largely been excluded from improvement efforts to date. For companies to better performance in ways that matter to their customers, they must know why customers buy from them in the first place. And once they do, why they keep coming back. This represents a shifting heirarchy of needs that often escapes the notice of companies trying to gain advantage in today's marketplace. This article outlines the stages of the customer‐supplier relationship and provides guidelines for companies that want to improve their performance in ways that will make their customers sit up and take notice.

Modern computer users must often sift and manage vast amounts of hierarchically structured information. However, conventional interface tools have not kept pace with the information explosion, leaving users with inadequate means to manage their data. This paper promotes ideas of information filtering and fisheye views of hierarchies through the use of dynamic queries. In particular, we present FLEXVIEW, a graphical system for visualizing file systems.