Researchers in the field of natural language processing are interestedin developing machines that can manipulate natural language and thereforelean in the engineering direction. Thus, linguists operate in simulation orientedmode—building systems whose goals are to test theories. In contrast, researchers in natural language processing operate in performance-oriented mode—building systems to perform tasks. Systems produced in this latter mode (such as document translators and systems by which machines respond to verbal commands) rely heavily on knowledge gained by linguists butoften apply “shortcuts” that happen to work in the restricted environment of the particular system.