The World Wide Web is a large, heterogeneous, distributed collection of documents connected by hypertext links. The most common technology currently used for searching the Web depends on sending information retrieval requests to "index servers" that index as many documents as they can find by navigating the network. One problem with this is that users must be aware of the various index servers (over a dozen of them are currently deployed on the Web), of their strengths and weaknesses, and of the peculiarities of their query interfaces. A more serious problem is that these queries cannot exploit the structure and topology of the document network. In this paper we propose a query language, WebSQL, that takes advantage of multiple index servers without requiring users to know about them, and that integrates textual retrieval with structure and topology-based queries. We give a formal semantics for WebSQL using a calculus based on a novel "virtual graph" model of a document network. We propose a new theory of query cost based on the idea of "query locality," that is, how much of the network must be visited to answer a particular query. We give an algorithm for characterizing WebSQL queries with respect to query locality. Finally, we describe a prototype implementation of WebSQL written in Java.

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Navigating and viewing large information spaces, such as hierarchically-organized networks from complex realtime systems, suffer the problems of viewing a large space on a small screen. Distorted-view approaches, such as fisheye techniques, have great potential to reduce these problems by representing detail within its larger context but introduce new issues of focus, transition between views and user disorientation from excessive distortion. We present a fisheyebased method which supports multiple focus points, enhances continuity through smooth transitions between views, and maintains location constraints to reduce the user’s sense of spatial disorientation. These are important requirements for the representation and navigation of networked systems in supervisory control applications. The method consists of two steps: a global allocation of space to rectangular sections of the display, based on scale factors, followed by degree-of-interest adjustments. Previous versions of the algorithm relied solely on relative scale factors to assign size; we present a new version which allocates space more efficiently using a dynamically calculated degree of interest. In addition to the automatic system sizing, manual user control over the amount of space assigned each area is supported. The amount of detail shown in various parts of the network is controlled by pruning the hierarchy and presenting those sections in summary form. KEYWORDS: graphical user interface, supervisory control systems, information space, hierarchical network, information visualization, fisheye view, navigation.

Making effective use of the available display space has long been a fundamental issue in user interface design. We live in a time of rapid advances in available CPU power and memory. However, the common sizes of our computational display spaces have only minimally increased or in some cases, such as hand held devices, actually decreased. In addition, the size and scope of the information spaces we wish to explore are also expanding. Representing vast amounts of information on our relatively small screens has become increasingly problematic and has been associated with problems in navigation, interpretation and recognition. User interface research has proposed several differing presentation approaches to address these problems. These methods create displays that vary considerably, visually and algorithmically. We present a unified framework that provides a way of relating seemingly distinct methods, facilitating the inclusion of more than one presentation method in a single interface. Furthermore, it supports extrapolation between the presentation methods it describes. Of particular interest are the presentation possibilities that exist in the ranges between various distortion presentations, magnified insets and detail-in-context presentations, and between detail-incontext presentations and a full-zooming environment. This unified framework offers a geometric presentation library in which presentation variations are available independently of the mode of graphic representation. The intention is to promote the ease of exploration and experimentation into the use of varied presentation combinations.

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When adjusting a graph layout, it is often desirable to preserve various properties of the original graph in the adjusted view. Pertinent properties may include straightness of lines, graph topology, orthogonalities and proximities. A layout adjustment algorithm which can be used tocreate sheye views of nested graphs is introduced. The SHriMP (Simple Hierarchical Multi-Perspective) visualization technique uses this algorithm to create sheye views of nested graphs. This algorithm preserves straightness of lines and uniformly resizes nodes when requests for more screen space aremade. In contrast to other layout adjustment algorithms, this algorithm has several variants to preserve additional selectedproperties of the original graph. These variants use di erent layout strategies to reposition nodes when the graph is distorted. The SHriMP visualization technique is demonstrated through its application to visualizing structures in large software systems.

This paper describes how our use of video artifacts affected the re-design of a graphical editor (Design/CPN) for building, simulating, and analyzing Coloured Petri Nets. The two primary goals of the project were to create design abstractions that integrate recent advances in graphical interaction techniques and to explicitly support the various patterns of using Petri Nets in real-world settings.

This paper presents the creation of a a visual environment for exploring landscape patterns and changes to such patterns over time. Dynamic landscape patterns can involve both spatial and temporal complexity. Exploration of spatio-temporal landscape patterns should provide the ability to view information at different scales to permit navigation of a vast amount of information in a manner that facilitates comprehension rather than confusion. One way of achieving this goal is to support selection, navigation and comparison of progressively refined segments of time and space. We have entitled this system Tardis after the time machine of Dr. Who, to emphasize the exploration of time dependent data and because our use of elastic presentation has the effect of providing more internal space than the external volume suggests. Of special concern in this research is the extent of the data and its inter-relationships that need to be understood over multiple scales, and the challenge inherent in i...

Most systems for visualizing large information structures use 2D graphics to view networks of nodes and arcs that represent data. To understand large structures it is often necessary to show both small-scale and large-scale structure. This has been called the problem of focus and context. Distortion, rapid zooming, elision, and multiple windows are all techniques that have been developed to provide both focus and context within single representations. We review these techniques and argue that 3D visualization has a number of advantages. A system called NestedVision3D (NV3D) will be presented that has been developed to investigate the use of 3D visualization for understanding the structure of large computer programs. NV3D is a system for visualizing large nested graphs using interactive 3D graphics. It has been tested with graphs containing more than 35,000 nodes and 100,000 relationships. We describe NV3D and its design philosophy. Basic navigation is facilitated by a set of 3D widget...

Software programs, especially legacy programs, are often large, complex and poorly documented. To maintain these programs software engineers require a variety of efficient analytical tools. Some software maintenance tools use visualizations (i.e. graphical views) to communicate information about software systems. Although many software visualization tools exist, the majority of them are not very effective in practice. Part of the problem is that they are designed in an ad hoc manner, with little empirical evaluation. They are often criticized because they try to force programmers to use a specific approach to understanding software rather than supporting their own approaches. The result is that current software visualization tools do not play as big a role in industry as was anticipated by some researchers. The tools that are used are very basic, consisting of mainly text editors and searching features. With increasingly fast computing platforms, there is great potential for the use of...