Combining Qualitative and Quantitative Temporal Reasoning for Criminal Forensics ∗ Abbas K. Zaidi, Mashhood Ishaque, and Alexander H. Levis Abstract The paper presents an application of temporal knowledge representation and reasoning techniques to forensic analysis, especially in answering certain inves- tigative questions relating to time-sensitive information about a criminal or terrorist activity. A brief introduction to a temporal formalism called Point-Interval Logic is presented. A set of qualitative and quantitative temporal facts is taken from the London bombing incident that took place on July 7, 2005, to illustrate the use of temporal reasoning for criminal forensics. The information used in the illustration is gathered through the online news sites. A hypothetical investigation on the infor- mation is carried out to identify certain time intervals of potential interest to counter- terrorist investigators. A software tool called Temper that implements Point-Interval Logic is used to run the analysis and reasoning presented in the paper. 1 Introduction While a sequence of events may unfold linearly in time, information about it comes in segments from different locations at different times, often overlapping and of- ten with small contradictions. This phenomenon occurs at a centralized information gathering node where information can be analyzed and fused both because of the Abbas K. Zaidi System Architectures Lab, George Mason University, Fairfax, VA 22030, e-mail: szaidi2@gmu. edu Mashhood Ishaque System Architectures Lab, George Mason University, Fairfax, VA 22030, e-mail: ADD-EMAIL Alexander H. Levis System Architectures Lab, George Mason University, Fairfax, VA 22030, e-mail: alevis@gmu.edu ∗ An earlier version of the paper has appeared in the proceedings of Descartes Conference on Mathematical Models in Counterterrorism, Center for Advanced Defense Studies, Washington DC, 2006. 63 Preliminary version (compiled by Claus Atzenbeck) – January 14, 2009 – 15:08