Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item Knowledge Discovery in High Dimensional Data: Case Studies and a User Survey for an Information Visualization Tool(2005) Seo, Jinwook; Shneiderman, Ben; ISRKnowledge discovery in high dimensional data is a challenging enterprise, but new visual analytic tools appear to offer users remarkable powers if they are ready to learn new concepts and interfaces. Our 3-year effort to develop versions of the Hierarchical Clustering Explorer (HCE) began with building an interactive tool for exploring clustering results. It expanded, based on user needs, to include other potent analytic and visualization tools for multivariate data, especially the rank-by-feature framework. Our own successes using HCE provided some testimonial evidence of its utility, but we felt it necessary to get beyond our subjective impressions. This paper presents an evaluation of the Hierarchical Clustering Explorer (HCE) using three case studies and an email user survey (n=57) to focus on skill acquisition with the novel concepts and interface for the rank-by-feature framework. Knowledgeable and motivated users in diverse fields provided multiple perspectives that refined our understanding of strengths and weaknesses. A user survey confirmed the benefits of HCE, but gave less guidance about improvements. Both evaluations suggested improved training methods.Item Domain Name Based Visualization of Web Histories in a Zoomable User Interface(2000) Gandhi, Rajiv; Kumar, Girish; Bederson, Benjamin B.; Shneiderman, Ben; ISRUsers of hypertext systems like the World Wide Web (WWW) often find themselves following hypertext links deeper and deeper, only to become "lost" and unable to find their way back to the previouslyvisited pages. We have implemented a web browser companion called Domain Tree Browser (DTB) that builds a tree structured visual navigation history while browsing the web. The Domain Tree Browser organizes the URLs visited based on the domain name of each URL and shows thumbnails of each page in a zoomable window. A usability test was conducted with four subjects.Item A Distributed Shared Key Generation Procedure Using Fractional Keys(1998) Poovendran, R.; Corson, M. Scott; Baras, John S.; ISR; CSHCNWe present a new class of distributed key generation and recoveryalgorithms suitable for group communication systems where the groupmembership is either static or slowly time-varying, and must be tightlycontrolled.The proposed key generation approach allows entities whichmayhave only partial trust in each other to jointly generate a shared keywithout the aid of an external third party. The group collectivelygenerates and maintains a dynamic group parameter, and the shared key isgenerated using a strong, one-way function of this parameter.
This schemealso provides perfect forward secrecy. The validity of key generation canbe checked using verifiable secret sharing techniques. The key retrievalmethod does not require the keys to be stored in an external retrievalcenter.
We note that many Internet-based applications may have theserequirements. Fulfillment of these requirements is realized through theuse of fractional keys--a distributed technique recently developed toenhance the security of distributed systems in a non-cryptographicmanner.
Item Data Object and Label Placement for Information Abundant Visualizations(1998) Li, Jia; Plaisant, Catherine; Shneiderman, Ben; ISRPlacing numerous data objects and their corresponding labels in limited screen space is a challenging problem in information visualization systems. Extending map-oriented techniques, this paper describes static placement algorithms and develops metrics (such as compactness and labeling rate) as a basis for comparison among these algorithms. A control panel facilitates user customization by showing the metrics for alternative algorithms. Dynamic placement techniques that go beyond map-oriented techniques demonstrate additional possibilities. User actions can lead to selective display of data objects and their labels.Item Design and Evaluation of Incremental Data Structures and Algorithms for Dynamic Query Interfaces(1997) Tanin, Egemen; Beigel, Richard; Shneiderman, Ben; ISRDynamic query interfaces (DQI) are a recently developed database access mechanism that provides continuous real-time feedback to the user during query formulation. Previous work shows that DQI are an elegant and powerful interface to small databases. Unfortunately, when applied to large databases, previous DQI algorithms slow to a crawl. We present a new incremental approach to DQI algorithms that works well with large databases, both in theory and in practice.Item Browsing Hierarchical Data with Multi-Level Dynamic Queries and Pruning(1995) Kumar, Harsha P.; Shneiderman, B.; ISR; CSHCNUsers often must browse hierarchies with thousands of nodes in search of those that best match their information needs. The tree-browser visualization tool was specified, designed and developed for this purpose. This tool presents trees in two tightly-coupled views, one a detailed view and the other an overview. Users can use dynamic queries, a method for rapidly filtering data, to filter nodes at each level of the tree. The dynamic query panels are user-customizable. Subtrees of unselected nodes are pruned out, leading to compact views of relevant nodes.The software architecture, data structures and algorithms used to achieve this behavior are specified. Usability testing of the Tree-browser, done with 8 subjects, helped assess strengths and identify possible improvements. The Tree-browser was applied to the Network Management (600 nodes) and UniversityFinder (1100 nodes) application. Future research directions are suggested.
Item Improving the Visualization of Hierarchies with Treemaps: Design Issues and Experimentation(1992) Turo, D.; Johnson, Brian; ISRControlled experiments with novice treemap users and real data highlight the strength of treemaps and provide direction for improvement. Issues discussed include experimental results, layout algorithms, nesting offsets, labeling, animation and small multiple displays. Treemaps prove to be a potent tool for hierarchy display. The principles discussed are applicable to many information visualization situations.