  This paper describes principles and practices of knowledge engineering that
enable the development of holistic language-endowed intelligent agents that can
function across domains and applications, as well as expand their ontological
and lexical knowledge through lifelong learning. For illustration, we focus on
dialog act modeling, a task that has been widely pursued in linguistics,
cognitive modeling, and statistical natural language processing. We describe an
integrative approach grounded in the OntoAgent knowledge-centric cognitive
architecture and highlight the limitations of past approaches that isolate
dialog from other agent functionalities.
