*_Notice and Invitation_* Oral Defense of Doctoral Dissertation The Volgenau School of Engineering, George Mason University *Mohammad Ababneh* Bachelor of Science, Mu'tah University, 1994 Master of Science, Naval Postgraduate School, 2000 A Dynamic Dialog System Using Semantic Web Technologies Thursday, 01/16/2014, 11:00AM Room 4801, Engineering Building All are invited to attend. *_Committee_* Dr. Duminda Wijesekera, Chair Dr. Arun Sood Dr. Rao Mulpuri Dr. Paulo Costa *_Abstract_* A dialog system or a conversational agent provides a means for a human to interact with a computer system. Dialog systems use text, voice and other means to carry out conversations with humans in order to achieve some objective. Most dialog systems are created with specific objectives in mind and consist of pre-programmed conversations. The primary objective of this dissertation is to show that dialogs can be dynamically generated using semantic technologies. I show the feasibility by constructing a dialog system that can be specific to control physical entry points, and that can withstand an attempt to misuse the system by playing back previously recorded conversations. As a solution my system randomly generates questions with a pre-specified difficulty level and relevance, thereby not repeating conversations. In order to do so, my system uses policies to govern the entrance rules, and Item Response Theory to select questions derived from ontologies relevant to those policies. Furthermore, by using contextual reasoning to derive facts from a chosen context, my dialog system can be directed to generate questions that are randomized within a topic, yet relevant to the task at hand. My system design has been prototyped using a voice interface. The prototype demonstrates acceptable performance on benchmark data. A copy of this doctoral dissertation is on reserve at the Johnson Center Library.