Wolter, M., Assenmacher, J., Hentschel, B., Shirski, M., & Kuhlen, T. (2009). A Time Model for Time-Varying Visualization. Computer Graphics Forum, 28(6), 1561–1571.
In 2009 existing frameworks for dealing with complex, real-world temporal data treated time as a simple, continuous, linear dimension—essentially a fourth spatial coordinate to be mapped or animated sequentially.