A timeline is a linear, graphical visualization of events over time. For example, in concurrent application, events would represent state changes for some system object (such as a task or variable). A timeline display generator creates the graphical visualization from some record of events. This paper reports on a model for timeline display generators based on a formal model of event history and the objectives of timeline visualization. In this model, any timeline display generator is completely described through the definition of a set of mathematical functions. The exact characteristics and flexibility of a particular implementation of a timeline display generator, depends on the way in which these functions have been implemented. The current prototype, xtg, (Timeline Display Generator for X-windows) serves as an example implementation of these ideas. Characteristics of xtg are presented, and its use in the analysis of a real-world client-server application is discussed. Xtg has been applied to several other applications to-date and is being applied by several telecommunications companies to areas ranging from software process analysis to call trace data analysis.
G.M. Karam (1994) studied this question.