The architecture of the control and data structures of the real-time expert system ERIK ("evaluating reports using integrated knowledge") is fine tuned for the task of flexible knowledge-intensive interpretation of ship messages. In spite of the large amounts of knowledge needed for this interpretation task, ERIK can interpret noisy and ill-formed inputs with high reliability due to a variety of computational features. Among these features are an expectation-driven control structure, selective variable depth focusing of attention, intelligent recovery from failed expectations, distributed recognition modules, and a sophisticated spelling correction facility. ERIK, which is now running on-line at the Coast Guard Automated Mutual-assistance Vessel Rescue (AMVER) center, incorporates artificial intelligence design and programming techniques. Using these techniques to solve a complex real-time information processing problem has led to theoretical and practical insights that are presented in this paper.