Reasoning about time in multiplayer games is not easy, especially if players are allowed to disengage and reengage at will. To facilitate such reasoning, Benford and Giannachi propose temporal trajectories that map story time against clock time. A canonical trajectory expresses the game author’s intent for the temporal structure of the game, while a participant trajectory describes where a player actually is in story time, as clock time unfolds.

Several figures illustrate the power of this diagrammatic approach. Figure 4 is used to describe the various ways in which a player’s disengagement and reengagement can be handled, including cases where a player drops out to play a local version of the game. Figure 8 helps describe the various ways in which two players can encounter one another and suggests new possibilities for gameplay. For example, a time portal could be used to allow information flow between players who are on the same clock time, but different story times. Figure 9 deals with accessing recorded events from the past and succeeds in making clear even the scenario where a player views a recording of himself viewing a recording. Any reader would find it difficult to fault the authors’ conclusion that temporal trajectories enable diagrammatic reasoning about temporal issues in multiplayer games.

Although Benford and Giannachi concede that they fall short of a truly comprehensive framework, their temporal trajectories currently present the best way to reason about time in multiplayer games. I strongly recommend this paper to the academic and commercial gaming sector.