This work found that explanations of global scene activity, particularly where interesting events had occurred, was achieved using an extensible, rule-based method. This paper was concerned with producing high-level text reports and explanations of human activity in video from a single, static camera, with the motivation being to enable surveillance analysts to maintain situational awareness despite the presence of large volumes of data. The scenario that the paper focused on was urban surveillance where the imaged person was depicted in medium/low resolution. The final output sought was text descriptions that not only described, in human-readable terms, what was happening but also explained the interactions that took place. The input to the reasoning process was said to be the information obtained from video processing methods that provided an abstraction from the image data to qualitative (i.e. human-readable) descriptions of observed human activity. The article also states that the complete system represents a general technique for video understanding, which requires a guided training phase by an experienced analyst. Figures, references