Despite intense and wide-spread research in both virtual environments (VEs) and usability, the exciting new technology of VEs has not yet been closely coupled with the important characteristic of usability --- a necessary coupling if VEs are to reach their full potential. Although numerous methods exist for usability evaluation of interactive computer applications, these methods have well-known limitations, especially for evaluating VEs. Thus, there is a great need to develop usability evaluation methods and criteria <i>specifically</i> for VEs. Our goal is to increase awareness of the need for usability engineering of VEs and to lay a scientific foundation for developing high-impact methods for usability engineering of VEs. The first step in our multi-year research plan has been accomplished, yielding a comprehensive multi-dimensional taxonomy of usability characteristics specifically for VEs. This taxonomy was developed by collecting and synthesizing information from literature, conferences, World Wide Web (WWW) searches, investigative research visits to top VE facilities, and interviews of VE researchers and developers. The taxonomy consists of four main areas of usability issues: <i> Users and User Tasks in VEs</i>, <i>The Virtual Model</i>, <i>VE User Interface Input Mechanisms</i>, and <i>VE User Interface Presentation Components</i>. Each of these issues is progressively disclosed and presented at various levels of detail, including specific usability suggestions and context-driven discussion that include a number of references. The taxonomy is a thorough classification, enumeration, and discussion of usability issues in VEs that can be used by VE researchers and developers for usability assessment or simply design. The author can be reached through <a href=http://csgrad.cs.vt.edu/~jgabbard/>http://csgrad.cs.vt.edu/~jgabbard/</a> / Master of Science

Although research and practice have shown that the success of a usability engineering program depends on the identification and correction of usability problems, these problems remain an underutilized source of information. Insufficient guidance regarding the capture of usability problem data results in the loss of information during the problem reporting phase as problem reports are often vague, imprecise, and incomplete. In addition, the absence of a framework for understanding, comparing, categorizing, and analyzing those problems, and their relationship to development context, not only constrains product improvement, but hampers efforts to improve the user interface development process. A new taxonomic model (the Usability Problem Taxonomy) is presented which contributes to both product and process improvement. The Usability Problem Taxonomy (UPT) is used to classify and organize usability problems detected on interactive software development projects. Individual UPT categories are associated with two aspects of development context: developer roles and skills, and development activities, methods, and techniques. Two studies were conducted during the course of this research. The first study showed that the UPT can be used to classify usability problems reliably. Findings indicated that level of agreement among classifiers (beyond chance agreement) was statistically significant. Findings in the second study led to the identification of roles and activities that address individual UPT categories as well as those that do not. Procedures for using the UPT in both product and process improvement are outlined. Examples are presented that illustrate how the UPT can be used to generate higher quality problem descriptions and to group those problem descriptions prior to prioritization and correction. In addition, steps that guide developers in diagnosing weaknesses in the current user interface development process are enumerated. Possible improvement strategies are presented that focus on the selection of specific development activities and team members appropriate for a given project. / Ph. D.