Temporal Trajectories in Shared Interactive Narratives Steve Benford Mixed Reality Laboratory University of Nottingham Nottingham, UK, NG81BB sdb@cs.nott.ac.uk Gabriella Giannachi Centre for Intermedia, Department of Drama University of Exeter Exeter, EX44LA, UK G.Giannachi@exeter.ac.uk ABSTRACT Temporal trajectories can represent the complex mappings between story time and clock time that are to be found in shared interactive narratives such as computer games and interactive performances. There are three kinds. Canonical trajectories express an author’s intended mapping of story time onto clock time as part of the plot and schedule of an experience. Participant trajectories reflect a participant’s actual journey through story time and clock time as they interact with the experience. Historic trajectories represent the subsequent selection and reuse of segments of recorded participant trajectories to create histories of past events. We show how temporal trajectories help us analyse the nature of time in existing experiences and can also generate new approaches to dealing with temporal issues such as: disengagement and reengagement, adapting to different paces of interaction, synchronising different participants, and enabling encounters and travel across time. Author Keywords Time, narrative, pacing, synchronization, disconnection, history, storytelling, games, hypermedia, entertainment, learning, drama, CSCW, mobile, SMS, plot, trajectory. ACM Classification Keywords H.5.3 [Information Systems] Group and Organization Interfaces – Collaborative Computing. INTRODUCTION The relationship between time and interaction has been a longstanding concern within HCI, spanning wide ranging discussions of responsiveness, pace and interaction [5], revealing and communicating delays [18], synchronising multiple users’ interactions [14,19], and visualizing, browsing and synchronising convergent and divergent histories of interaction [8,9,17]. This paper extends HCI’s concern with time to address the challenges raised by a new generation of narrative-driven experiences such as computer games, artistic performances and hypermedia stories. A distinctive feature of such experiences is that an author first creates an underlying narrative, a guiding temporal structure for events that drives the experience. Participants subsequently interact with this structure at different times according to their desire and availability. We can see examples of this in current computer games. Single player computer games typically provide players with very flexible control over time and pacing. They can pause and resume the game’s narrative at their convenience and can move backwards and forwards in game time, replaying previous levels. Game time may also be flexibly sped up or slowed down as in simulation games where players pause the game to make changes to the simulation and then rapidly advance time to see them played out. In contrast, Massively Multiplayer Online Role Playing Games (MMORPGS) tend to adopt a more seemingly objective approach to time. Here, groups of players share a common narrative timeline that progresses linearly in relation to clock time, often advancing even when they are not playing. This gives each individual far less control over the progression of the narrative but enables players to share a social experience. An emerging generation of mobile experiences further complicates this picture as participants rapidly dip in and out of an experience while on the move, engaging in the ‘downtime’ between other activities, being subject to frequent disconnections and reconnections, and fitting the experience to the patterns of their daily lives [2]. A further interesting characteristic of time in narrative- driven experiences is the participants’ desire to experience or tell stories of what happened to them in the past, replaying highlights, reviewing histories, drawing on recordings of their interactions to make animations and videos, and even mixing live experiences with recordings of previous ones (e.g., the Gran Turismo racing game in which players can race against previous versions of themselves). In short, designing the temporal structure of a shared interactive narrative is a complex business that raises new and difficult challenges for HCI. How can we negotiate the pace and timing of interaction between authors who wish to impose a driving narrative and participants who wish to experience this at times that suit them? How can participants fit an ongoing long-term narrative into the patterns of their daily lives, flexibly engaging and disengaging as required? How can we extend this Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. CHI 2008, April 5–10, 2008, Florence, Italy. Copyright 2008 ACM 978-1-60558-011-1/08/04…$5.00. CHI 2008 Proceedings · Stories and Memories April 5-10, 2008 · Florence, Italy 73