Generative design systems make it easier for designers to generate and explore design alternatives, but the amount of information generated during a design session can become very large. Intelligent navigation aids are needed to enable designers to access the information with ease. Such navigation aids may improve the usability of generative design systems and encourage their use in the architectural design practice.

This dissertation presents a comprehensive approach to support navigation in generative design systems. This approach takes account of studies related to human spatial cognition and wayfinding in physical environments as well as information navigation in electronic media. It contains a general model of the design space, a set of basic navigation operations, and some principles for designing navigation support. The general model of the design space--the information space of generative design systems--describes how the space may grow and evolve along predictable dimensions, which, unlike the dimensions or axes of a Cartesian coordinate space, are interdependent. The set of basic operations facilitates navigation activities in this multi-dimensional design space. The design principles aim at guiding system developers in creating navigation utilities that are tailored to the needs of individual generative design systems.

This approach is validated through prototype implementations and limited pilot usability studies of the prototypes. The validity of the design space model and basic navigation operations is examined through the development of a design space navigation framework that encapsulates the model and operations in a software environment and provides the infrastructure and mechanisms for supporting navigation. Three prototype navigation tools for a two-dimensional schematic layout design system are implemented using this navigation framework. These tools are subjected to several usability studies: an empirical study to evaluate their usability, a formal usability analysis and user tests to assess specific aspects of their functionality. The usability studies show that these navigation tools are easy to learn and are efficient in assisting designers locating desired information; conversely, designers may feel lost or confused when lacking navigation support. In summary, it can be demonstrated that through the prototype implementations and usability studies, this approach offers sufficient support for the design and implementation of navigation aids in a generative design system.

The research effort presented in this dissertation is a pioneer study on navigation support in generative design systems. The research has demonstrated why navigation support is necessary through an extensive literature survey and the results from usability studies of several prototype navigation tools; how to provide the support through a general design space model and a set of basic navigation operations; and what type of user interaction navigation support can offer through these prototype navigation tools. This research contributes to information navigation studies not only in the specific domain of generative design system research, but also in the general field of human-computer interaction.

abstract PDF at http://code.arc.cmu.edu/lab/upload/98schien.0.pdf
main chapters (1.2M) http://code.arc.cmu.edu/lab/upload/nik-dissertation.0.pdf
appendices (1.1M) http://code.arc.cmu.edu/lab/upload/appendices.0.pdf

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