modeling

This paper describes a Computer Aided Design system for sketching free-form polygonal surfaces such as terrains and other natural objects. The user manipulates two 3D position and orientation trackers with three buttons, one for each hand. Each hand has a distinct role to play, with the dominant hand being responsible for picking and manipulation, and the less-dominant hand being responsible for context setting of various kinds. The less-dominant hand holds the workpiece, sets which refinement level that can be picked by the dominant hand, and generally acts as a counterpoint to the dominant hand. In this paper, the architecture of the system is outlined, and a simple surface is shown.

In this paper we present a method for helping artists make artwork more accessible to casual users. We focus on the specific case of drawings, showing how a small number of drawings can be transformed into a richer object containing an entire family of similar drawings. This object is represented as a simplicial complex approximating a set of valid interpolations in configuration space. The artist does not interact directly with the simplicial complex. Instead, she guides its construction by answering a specially chosen set of yes/no questions. By combining the flexibility of a simplicial complex with direct human guidance, we are able to represent very general constraints on membership in a family. The constructed simplicial complex supports a variety of algorithms useful to an end user, including random sampling of the space of drawings, constrained interpolation between drawings, projection of another drawing into the family, and interactive exploration of the family.

A new technique to enter text using a mobile phone keypad is described. For text input, the traditional touchtone phone keypad is ambiguous because each key encodes three or four letters. Instead of using a stored dictionary to guess the intended word, our technique uses probabilities of letter sequences --- "prefixes" --- to guess the intended letter. Compared to dictionary-based methods, this technique, called LetterWise, takes significantly less memory and allows entry of non-dictionary words without switching to a special input mode. We conducted a longitudinal study to compare LetterWise to Multitap, the conventional text entry method for mobile phones. The experiment included 20 participants (10 LetterWise, 10 Multitap), and each entered phrases of text for 20 sessions of about 30 minutes each. Error rates were similar between the techniques; however, by the end of the experiment the mean entry speed was 36% faster with LetterWise than with Multitap.

A central goal of many user interface development tools has been to make the construction of high quality interfaces easy enough that iterative design approaches could be a practical reality. In the last 15 years significant advances in this regard have been achieved. However, the evaluation portion of the iterative design process has received relatively little support from tools. Even though advances have also been made in usability evaluation methods, nearly all evaluation is still done “by hand,” making it more expensive and difficult than it might be. This paper considers a partial implementation of the CRITIQUE usability evaluation tool that is being developed to help remedy this situation by automating a number of evaluation tasks. This paper will consider techniques used by the system to produce predictive models (keystroke level models and simplified GOMS models) from demonstrations of sample tasks in a fraction of the time needed by conventional handcrafting methods. A preliminary comparison of automatically generated models with models created by an expert modeler show them to produce very similar predictions (within 2%). Further, because they are automated, these models promise to be less subject to human error and less affected by the skill of the modeler.

In this paper, we describe Augur, a groupware calendar system to support personal calendaring practices, informal workplace communication, and the socio-technical evolution of the calendar system within a workgroup. Successful design and deployment of groupware calendar systems have been shown to depend on several converging, interacting perspectives. We describe calendar-based work practices as viewed from these perspectives, and present the Augur system in support of them. Augur allows users to retain the flexibility of personal calendars by anticipating and compensating for inaccurate calendar entries and idiosyncratic event names. We employ predictive user models of event attendance, intelligent processing of calendar text, and discovery of shared events to drive novel calendar visualizations that facilitate interpersonal communication. In addition, we visualize calendar access to support privacy management and long-term evolution of the calendar system.

People use their awareness of others' temporal patterns to plan work activities and communication. This paper presents algorithms for programatically detecting and modeling temporal patterns from a record of online presence data. We describe analytic and end-user visualizations of rhythmic patterns and the tradeoffs between them. We conducted a design study that explored the accuracy of the derived rhythm models compared to user perceptions, user preference among the visualization alternatives, and users' privacy preferences. We also present a prototype application based on the rhythm model that detects when a person is "away" for an extended period and predicts their return. We discuss the implications of this technology on the design of computer-mediated communication.