Abstract: Beginning with the most fundamental persistence function, solutions were presented which involve expanding EXPRESS model using Object-oriented Modeling Technology; extending SDAI contents properly; achieving objects' self-supplied -O function; and implementing the object-oriented encapsulation and dynamic binding, on several key technologies such as the SDA C+ + management classes, the early/late binding data access methods and the combined early/late binding operations. Using these solutions, one prototype system is developed. The motive to carry out this system is to meet the need of the integration of CAx application systems based on STEP.