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Remembering David Carr


We were greatly disturbed to hear the sad news of David Carr's untimely death from a heart attack on Friday January 6, 2006. He was an Associate Professor of Human-Computer Interaction in the Dept of Computer Science & Electrical Engineering at Lulea University in Sweden.  His research contributions focused on information visualization and user interface development tools (see his recent papers at

David Carr was a doctoral student at the Human-Computer Interaction Lab and the Department of Computer Science at the University of Maryland from 1989-1995.  He was a memorable student who kept in touch with us through the years since his graduation.  We followed his work with great satisfaction, seeing him make important contributions in the fields of human-computer interaction and information visualization.  We regularly reference David's work and encourage colleagues to read his papers, which have a competent blend of technological implementation and rigorous empirical evaluations. 

He contacted me (Ben S.) just last month (December 2005) to write a reference letter for him, which I was pleased to do.  That letter reviewed his work over the years: "I especially appreciate his capacity for implementation of novel ideas and his diligence in conducting effective evaluation."  and concluded with this comment: "his high competence and reliable performance make him an asset to any project or team.  I am proud to have worked with him and am confident that he will continue to be a productive researcher."

It is tragic to think that David has died so young -- such things just shouldn't happen.  We will always appreciate his capable professional performance.  On a personal level our interactions with David were gentle and satisfying. He was a mature student and we talked about life and its challenges, during his stay at Univ. of Maryland and afterwards.  We were pleased with his decision to take the position at Lulea University and happy to hear of his marriage to Lenka Motycková, with whom he has co-authored five papers on reliable multicasting. 

David Carr's students also tell of their good experiences working with David; one of them sent a nice note: "David was a very dear friend as well as a mentor. He had a way of making his graduate students feel like family and could put whatever troubled you, professionally as well as personally into perspective."  

We especially appreciate his capacity for implementation of novel ideas and his diligence in conducting effective evaluations.  He was knowledgeable about diverse hardware/software systems and combined a solid computer science education (B.S. in Computer Science, Michigan Technological University (1975), M.S. in Computer and Communications Science, University of Michigan (1987), Ph.D. in Computer Science, University of Maryland (1995)) with substantial professional experience. 

His programming competence was strong and his capacity to deliver as promised and on time was admirable.  His high quality work has been an exemplar of excellence (modular design, efficient execution, and excellent documentation) and a positive influence on others in our lab.  David Carr’s work on our medical teleoperation project enabled us to create a novel system and useful empirical results.  This led to several papers including the widely cited 1995 IEEE Software paper: "Image-browser taxonomy and guidelines for designers."

David Carr's dissertation work developed a graphical formal specification method for user interface widgets.  The specification extended Harel’s statecharts, Hartson’s UAN, and others to produce a highly readable, compact notation.  His single-authored paper on this topic was presented at the prestigious ACM CHI’94 conference. 

David Carr was quieter than many students, but when he spoke he made thoughtful and creative contributions.  His papers were well organized, and he made his points clearly, helping to advance work in several areas of human-computer interaction. He kept in touch with colleagues from HCIL, exchanging views on the respective advantages of Europe and the US, or even helping us find bugs in our web pages just a few weeks ago while downloading the latest HCIL videos to use in his classes. We are saddened and shaken by his too young death.

Ben Shneiderman, with Catherine Plaisant
Human-Computer Interaction Laboratory

University of Maryland
January 10th, 2006

David Carr (second from the right) in a photo taken during the award ceremony of the Office of Technology Liaison in 1994.  An award was given to a team of HCILers (nicknamed the “Widget Carvers”) for their Widget Library.
From left to right: Marko Teittinen, Wayne Swann (director of OTL), Ilene H. Nagel (Associate Provost for Research and Dean of The Graduate School), Rick Chimera, Ben Shneiderman, William Destler (Senior Vice President for Academic Affairs and Provost), Ninad Jog, Dave Carr, and Richard Herman (Dean of CMPS).

Below are abstracts of the papers in our HCIL Tech Report database authored by David, including his PhD Thesis

Carr, D. (May 1995)
A Compact Graphical Representation of User Interface Interaction Objects
190 page Doctoral dissertation CSC 949, see 94-09 for condensed version.

The design of new user-interface interaction objects (or widgets) remains a laborious process. The designer must translate the proposed widget into a computer language and install it in the graphical user interface. This dissertation proposes an executable, graphical specification method to help solve this problem. After a review of previous methods used to specify user interfaces and widgets, the Interaction Object Graph (IOG) is introduced and defined. IOGs are a graphical specification method designed specifically for widgets. Example IOG specifications are given for many current widgets and for several new widgets. In addition, it is shown that an arbitrary Turing machine can be transformed into an IOG. Therefore, IOGs may be used to specify any widget. The dissertation also reports on a pilot experiment comparing IOGs with a text specification method, User Action Notation. This experiment gives a weak indication that graphical specifications such as IOGs are easier to understand. Finally, a C++ class library was implemented for executing IOG-specified widgets while animating the diagrams. The design of this library and the animated specification diagrams are discussed. IOGs extend statecharts with special states to represent display changes and with special nodes and arcs to model widget attribute updates. Display states are represented by a picture of the widget appearance. The picture improves IOG diagram readability by providing an idea of how the widget's appearance will change as the user operates the widget. Data nodes and arcs allow the widget designer to specify the relationship between user actions and widget attribute values. This capability can result in smaller specifications than methods without data modeling. It is also easier to locate all updates to a particular data item in an IOG than in methods that model change with equations annotating a state or column entry. Finally, in order to enhance specification understanding and debugging, the IOG class library animates an IOG diagram showing changes in the active states as the user operates the widget.

Carr, D., Jog, N., Kumar, H.P and Teittinen, M.
Using Interaction Object Graphs to Specify and Develop Graphical Widgets
HCIL-94-09 , CS-TR-3344 , CAR-TR-734, ISR-TR-94-69

This document describes five widgets that have been developed at the Human-Computer Interaction Laboratory of the University of Maryland. These widgets are: a range selection slider, a two-level alpha-slider, a secure switch, a tree viewer, and a treemap viewer. The last two use the same tree representation and can be used as alternate visualizations of the same hierarchy. In addition, a system for widget specification is introduced and each widget is specified using this system.

Carr, D., Plaisant, C. and Hasegawa, H.
Usability Experiments for the Redesign of a Telepathology Workstation
Based on The Design of a Telepathology Workstation: Exploring Remote Images.
Interacting with Computers, 11(1), 1998, pp. 33-52.
HCIL-94-03 , CS-TR-3270 , CAR-TR-708

Dynamic telepathology uses a remotely controlled microscope to allow a pathologist to view samples at a remote location. However, time delays introduced by remote operation have made use of a commercial dynamic telepathology system difficult and frustrating. This paper describes experiments to evaluate and redesign the user interface. We also make recommendations for further automation to support the pathology process and increase the usefulness of the system.

Plaisant, C., Carr, D. and Shneiderman, B.
Image Browsers: Taxonomy, Guidelines, and Informal Specifications
IEEE Software, vol.12, 2 (March 1995) 21-32.
HCIL-94-02 , CS-TR-3282 , CAR-TR-712, ISR-TR-94-39

Image browsing is necessary in numerous applications. Designers have merely used two one-dimensional scroll bars or they have made ad hoc designs for a two-dimensional scroll bar. However, the complexity of two-dimensional browsing suggests that more careful analysis, design, and evaluation might lead to significant improvements. We present a task taxonomy for image browsing, suggest design features and guidelines, assess existing strategies, and introduce an informal specification technique to describe the browsers.

Carr, D.
Specification of Interface Interaction Objects
ACM CHI '94 Conference Proc. (Boston, MA, April 24-28, 1994) 372-378.
HCIL-93-20 , CS-TR-3142 , CAR-TR-687

User Interface Management Systems have significantly reduced the effort required to build a user interface. However, current systems assume a set of standard "widgets" and make no provisions for defining new ones. This forces user interface designers to either do without or laboriously build new widgets with code. The Interface Object Graph is presented as a method for specifying and communicating the design of interaction objects or widgets. Two sample specifications are presented, one for a secure switch and the other for a two dimensional graphical browser. 

Plaisant, C., Carr, D. and Hasegawa, H. (Oct. 1992)
When an intermediate view matters: A 2D browser experiment
HCIL-92-13 , CS-TR-2980 , CAR-TR-645, SRC-TR-92-119.

The browsing of two dimensional images can be found in a large number of applications. When the image to be viewed is much larger than the screen available, a two dimensional browser has to be provided to allow users to access all parts of the image. We show the diversity of tasks and systems available and the need for 2D browser design guidelines. In the context of a microscope image browser, we investigate one common technique consisting of a global view of the whole image, coupled to a detailed, mag nified view of part of the image. In particular we look at the benefits of providing an intermediate view when the detail-to-overview ratio is high. An experiment showed that users performance significantly degrades when no intermediate view is provided for a detail-to-overview ratio over 20:1. Our experience is also a good example of a real world application for which added features and added hardware need to be justified. 

Carr, D., Hasegawa, H., Lemmon, D. and Plaisant, C.
The effects of time delays on a telepathology user interface
Proc. of the 16th Annual Symposium on Computer Applications in Medical Care , SCAMC (Baltimore, MD, Nov. 7-11, 1992) 256-260.
HCIL-92-05 , CS-TR-2874 , CAR-TR-616, SRC-TR-92-49.

Telepathology enables a pathologist to examine physically distant tissue samples by microscope operation over a communication link. Communication links can impose time delays which cause difficulties in controlling the remote device. Such difficulties were found in a microscope teleoperation system. Since the user interface is critical to pathologist's acceptance of telepathology, we redesigned the user interface for this system, built two different versions (a keypad whose movement commands operated by specifying a start command followed by a stop command and a trackball interface whose movement commands were incremental and directly proportional to the rotation of the trackball). We then conducted a pilot study to determine the effect of time dela ys on the new user interfaces. In our experiment, the keypad was the faster interface when the time delay is short. There was no evidence to favor either the keypad or trackball when the time delay was longer. Moving long distances over the microscope slide by dragging the field-of-view indicator on the touchscreen control panel improved inexperience user performance. Also, the experiment suggests that changes could be made to improve the trackball interface.


David Carr presents his paper "Specification of Interface Interaction Objects" at the ACM SIGCHI conference in Boston, MA in 1994. (Photo by Ben Shneiderman)

Former University of Maryland doctoral students Andrew Sears and David Carr share a quiet moment at the ACM SIGCHI conference in Pittsburgh, PA in 1999. (Photo by Ben Shneiderman)

HCIL retreat 1992: David (first from the left) with, on the ground: Teresa Casey (now Cronnell), Masakazu Osada, Ara Kotchian, Hiroaki Hasegawa, Chris Williamson, Catherine Plaisant; and in the tree: David Turo, Richard Potter, Andrew Sears, Rick Chimera and Brian Johnson upside down. The original caption was "Treemap gets to our heads".


You can also see David in one of the video demonstrations of the 1995 HCIL video.

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