The use of precedent cases for reference is probably a very common practice in industry even for experts because each previously completed case, whether a success or failure, constitutes a wealth of experience and expertise which is too invaluable to ignore. In addition, making use of precedent cases for references can cut down the time required for completing the new design, thereby increasing the productivity and the competitive edge of the designers. With this observation in mind, the approach of this study is to develop an integrated knowledge-based system which is capable of making use of both the precedent cases and the earned expertise. The system is called IPDOS, a knowledge-embedded database system for the preliminary design of offshore structures. In IPDOS, past successful design cases are represented in data files which can be easily retrieved by matching of the design parameters in the corresponding knowledge bases.