Appropriating new technologies in order to foster collaboration and participatory engagement is a focus for many fields, but there is relatively little research on the experience of practitioners who do so. The role of technology-use mediators is to help make such technologies amenable and of value to the people who interact with them and each other. When the nature of the technology is to provide textual and visual representations of ideas and discussions, issues of form and shaping arise, along with questions of professional ethics. This thesis examines such participatory representational practice, specifically how practitioners make participatory visual representations (pictures, diagrams, knowledge maps) coherent, engaging and useful for groups tackling complex societal and organizational challenges. This thesis develops and applies a method to analyze, characterize, and compare instances of participatory representational practice in such a way as to highlight experiential aspects such as aesthetics, narrative, improvisation, sensemaking, and ethics. It extends taxonomies of such practices found in related research, and contributes to a critique of functionalist or techno-rationalist approaches to studying professional practice. It studies how fourteen practitioners using a visual hypermedia tool engaged participants with the hypermedia representations, and the ways they made the representations matter to the participants. It focuses on the sensemaking challenges that the practitioners encountered in their sessions, and on the ways that the form they gave the visual representations (aesthetics) related to the service they were trying to provide to their participants. Qualitative research methods such as grounded theory are employed to analyze video recordings of the participatory representational sessions. Analytical tools were developed to provide a multi-perspective view on each session. Conceptual and normative frameworks for understanding the practitioner experience in participatory representational practice in context, especially in terms of aesthetics, ethics, narrative, sensemaking, and improvisation, are proposed. The thesis places these concerns in context of other kinds of facilitative and mediation practices as well as research on reflective practice, aesthetic experience, critical HCI, and participatory design
