Sharing information between diverse heterogeneous databases and users has become one of the common goals of ontology-based systems. Several commercial endeavors have been successful, such as Yahoo! with taxonomies for categorizing websites and Amazon.com for categorizing products, respectively. However, large legacy databases raise many challenges. The data base schemas are often poorly designed and the metadata is poorly documented. Rarely is there a standard vocabulary for describing entities. Ontology can be developed for databases, but mappings between legacy databases remains one of the grand challenges. This paper addresses some of these issues in context of homeland security.