CORDTRA stands for Chronological-Ordered Representation of Discourse or Tool Related Activity. These diagrams consist of a timeline where multiple processes are ploted in parallel. Basically it is scatter plot where activities follow a certain coding scheme. In my example the usage of video annotations was distinguished into different interactions, e.g. using Popcorn Maker or direct annotation authoring or contributing/starting an electronic assessment (quiz). The input data was captured in a logfile containing activity data together with a unix time stamp.