I work on artificial intelligence with emphasis on building applied systems that make use of knowledge when devising their actions. In this pursuit I use principled, mathematical tools from logic, probability theory, and decision theory together with insights from cognitive science. Technically, my effort focuses on automatic reasoning, representing and using commonsense knowledge and relational uncertain knowledge, autonomous agent control and architectures, planning and rational decision making, and learning explicit knowledge in dynamic settings. I am also interested in graph algorithms, building large commonsense knowledge bases, and reactive systems. I am interested in applications of those in robotics, machine learning, vision, virtual worlds, and computer games, and building human-level AI programs.