A full mission simulator, just as the device it simulates, consists of many different subsystems, each of which requires a uniquely formatted data base. Creating each of these data bases individually can be expensive and time consuming. Another problem to be solved is the correlation or interoperability of data bases. Although the formats for each subsystem (e.g. visual, sensor, moving map, etc.) are different, the data in each must correlate to some degree with all other simulation subsystems. Just as each simulator must correlate the various subsystems, a simulation facility must provide the capability to correlate each subsystem of one simulator with the comparable ones on other simulators. This paper will discuss the methodology used at McDonnell Douglas Helicopter Company to handle data base conversion between our many simulation systems. We will also examine many questions and issues that need to be discussed prior to developing correlatable (interoperable) data bases.