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Article

Vol.30 No.2, April 1998

Article

Issue

Graphical User Interfaces For Hierarchies

Workshop Summary

Louis C. Vroomen

Hierarchical classification is a basic cognitive model used in almost all fields and in all cultures. Hierarchies are used for information organization about libraries, computer directories, stock portfolios, demographics, and many more resources. Textual representations with nesting and indenting to show levels are popular, but novel graphical approaches with node-link diagrams, cone trees, hyperbolic trees, and treemaps are expanding the choices for designers and users. Some of the key issues for researchers and developers are:

Structure: dealing with high fan-out or depth
2D versus 3D
Static (panning and zooming) vs. dynamic representations (pruning)
Navigation: Where did I come from, where am I and where can I go to?
Tasks: viewing, navigating, exploring, probing/searching, locating, filtering, editing, etc.
Media limits: physical resolution and chromatic resolution
Test datasets and tasks.

Both the University of Maryland Human-Computer Interaction Laboratory (HCIL) and the Centre de Recherche Informatique de Montréal (CRIM) have been working on this topic for some time. In order to explore the current state of hierarchical representation, we organized a two-day workshop for researchers and advanced developers. We wished to ensure an open atmosphere with focused interaction, and therefore limited the range of topics and number of attendees.

We invited a few people we knew to be working in the field and a notice on CHI-ANNOUNCEMENTS generated many interesting additions (see program below). Over 20 people, from university, government and industry, participated in the workshop, with good representation from cognitive science, visualization and applications domains. The workshop had a modest international flavor with participants coming from Austria, England, Israel, Canada and the United States.

Summary

Steve Feiner provoked a continuing debate, with his opening speech, "Trick or Tree: The Role of Hierarchy in the User Interface". Deftly reminding the participants that hierarchies are not necessarily trees, the path was open for spirited discussions on this complex issue. Experts in cognitive sciences painted a portrait of the problem. Visualization experts presented potential solutions. And then these were reconsidered in the light of the experiences presented by the experts from industry.

Lively discussions ensued on topics such as metrics, taxonomies, mapping versus manipulation, and ontology.

Some of the main issues discussed were:

Within hierarchical representation, there are few metrics to guide research and development. There seems to be little indication of the human requirements in this area. And what metrics do exist, such as how much time is required to get to a point, seem artificial.
Most research is in the visual representation of hierarchies, yet there are few tools to assist sophisticated access to these representations. The mapping of hierarchies has overshadowed the manipulation of them. As the data becomes more complex users require widgets to dynamically access information. Success depends on a clear integration of mapping and manipulation.
Navigation issues are an important area to continue investigating. We need to thoroughly understand the user who contemplates "where did I come from, where am I and where can I go to?" A good solution requires the support of an adaptive history management. Additionally many of the current solutions do not adequately exploit the underlying data. Landmarks, personality of data, neighborhood information need to be exploited to aid the user in navigation.
Correlation of elements within the structure is lacking. Users can discriminate but often they need to correlate the elements. For example, the user may need to know which elements are closely related to each other within the hierarchy. More research is required to provide tools to aid in this task.

Many other points were brought up over the two days. Participants held spirited discussions during the catered lunches and continued through vigorous afternoon walks about the campus. The discussions, for many, continued in the evening, at a nearby restaurant. The good food, wine, beer and coffee helped us extend the collegial workshop atmosphere as we established new professional collaborations.

The workshop website provides information and links: http://www.crim.ca/~vroomen/workshop/workshop.htm

Program: Day 1

Opening Speech: Trick or Tree: The Role of Hierarchy in the User Interface
Steven K. Feiner,
Columbia University
feiner@cs.columbia.edu

Hierarchical Spatial Reasoning
Adrijana Car,
Technical University Vienna
car@geoinfo.tuwien.ac.at

Inclusive Selection Tasks in Hierarchies and Database Thesauri: Inherent Difficulties and Prospects for User Interface Designs
Mark Treglown,
University of Bristol
Mark.Treglown@bristol.ac.uk

Navigation through Multimodal Hierarchical Spaces
Stephen Hirtle,
University of Pittsburgh
sch@sis.pitt.edu

Treemaps for Novices: Improving comprehensibility by refining visual design
Ben Shneiderman,
University of Maryland
ben@cs.umd.edu

Keynote Address: VLSI for the Hyperbolic Tree (Very Large Scale Impact:-)!
Ramana Rao,
Inxight Software (by phone)
rao@parc.xerox.com

Benchmarking interactive systems: efforts at NIST and how they relate to visualization
Sharon Laskowski
The National Institute of Standards and Technology
sharon.laskowski@nist.gov

Presenting Hierarchical Information in 3D Worlds
Michelle Zhou,
Columbia University
zhou@cs.columbia.edu

Visual elision: A technique to represent and explore complex hierarchies
Luc Beaudoin,
Centre de recherche informatique de Montréal
Luc.Beaudoin@crim.ca

Day 2

GIZA: A framework for visualization
Louis Vroomen & Marc-Antoine Parent,
Centre de recherche informatique de Montréal
vroomen@crim.ca ,
maparent@crim.ca

Animated Multiscale Interactive Treebrowsing
Kent Wittenburg,
GTE Laboratories
kentw@gte.com

Containerization for hierarchies
Douglas Talbott
Nortel
Doug.Talbott.talbott@nt.com

Interface Widgets for Manipulating Hierarchies
Catherine Plaisant & Ben Shneiderman,
University of Maryland
plaisant@cs.umd.edu ,
ben@cs.umd.edu

Lexicon Cruiser for Exploring Semantic Neighborhoods
Rich Mushlin,
IBM Research
mushlin@watson.ibm.com

Browsing Digital Libraries: A case study of the Library of Congress and WebTOC
Dave Nation,
Defense Department, Visiting Xerox PARC
dnation@parc.xerox.com
Catherine Plaisant,
University of Maryland
plaisant@cs.umd.edu

Organizers

Ben Shneiderman,
ben@cs.umd.edu

Catherine Plaisant,
plaisant@cs.umd.edu

Anne Rose,
rose@cs.umd.edu

Human-Computer Interaction Laboratory
University of Maryland
College Park, MD 20742 USA

Luc Beaudoin
lubeaudo@crim.ca

Louis Vroomen
vroomen@crim.ca

Marc-Antoine Parent
maparent@crim.ca

Human-Computer Interaction Group
Centre de Recherche Informatique de Montréal
Montréal, Qc, Canada, H3A 2N4

Additional Attendees

Nahum Gershon,
The MITRE Corp.
gershon@mitre.org

Kent L. Norman,
University of Maryland
kn8@umail.umd.edu

David Rashty,
Hebrew University of Jerusalem
rashty1@sunsite.cc.huji.ac.il

Barry Vaughan,
Johns Hopkins University
barry_vaughan@jhu.edu

About the Author

Louis C. Vroomen is an advisor/consultant at the Centre de recherche informatique de Montréal (CRIM), in the Human Computer Interaction group. He has been working at CRIM since 1987 in speech understanding, user interface design and visualization of complex data.

Author's Address

Louis C. Vroomen
1801 McGill College, Suite 800
Montréal, Quebec
Canada H3A 2N4

email: vroomen@crim.ca
URL: http://www.crim.ca/~vroomen

Tel: +1-514- 840-1234

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Vol.30 No.2, April 1998
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