While interactive design tools, rapid prototyping tools, and user interface management systems (UIMSs) are advancing as cost-effective ways of producing interfaces, attention to usability is rarely incorporated into such tools. The advancement of producing interfaces more rapidly without addressing their quality is of limited worth. This thesis reports on the design and prototype implementation of a software tool, IDEAL (Interface Design Environment and Analysis Lattice), that encourages and enables user-centered design as an integral part of the user interface development process. IDEAL integrates usability engineering techniques and behavioral task representations with a graphical hierarchy of associated user tasks to support formative evaluation of an evolving user interface. IDEAL supplements the functionality of current interface construction tools by focusing on usability through user-centered design. IDEAL was designed and developed using the techniques it supports: formative evaluation and iterative refinement. Representative users participated in two phases of qualitative formative evaluations from which critical incidents, verbal protocol, and qualitative data were collected. Feedback from each phase contributed to the revised design of IDEAL. This empirical evaluation showed IDEAL to be useful as an automated tool for managing the interrelated tasks of interface development, including design, usability specification definition, and formative evaluation, that are currently performed manually (e.g., using pencil and paper.) / Master of Science