ABSTRACT
The strategy adopted in the author's investigation of the feasibility of constructing a unified data base of educational data was simply to try to merge several data bases on a small scale to see what problems would be encountered. If no unsolvable problems were encountered, we then would proceed with a pilot model of a unified base and run it on sample tasks as a way of estimating costs and evaluating the output obtained. The fact is that we never reached the pilot model stage, for reasons that are made evident shortly. To describe the problems encountered in constructing a unified data base and using national data bases in educational research, and simultaneously to convey our conclusions about the feasibility of the former, we review the strengths and weaknesses of each of the levels of unified data bases that we described earlier.
