The invention establishes the context in which data exchanged between dissimilar relational database management systems can be mutually understood and preserved. The invention accomplishes this by establishing layers of descriptive information which isolate machine characteristics, levels of support software, and user data descriptions. Optimized processing is achieved by processing the different descriptor levels at different times during the development and execution of the database management systems. Minimal descriptive information is exchanged between the cooperating database management systems. For systems which match, data conversion is completely avoided. For systems which do not match, data conversion is minimized.