In this paper we discuss the applicability of the knowledge representation and reasoning language AnsProlog (Answer Set Programming) for the design and implementation of a query answering system (QAS) for homeland security. We discuss our work to date on using AnsProlog to axiomatize the travel domain. We illustrate how it can be used to represent defaults, causal relations, and other types of commonsense knowledge needed to properly answer non-trivial questions about this domain