High Quality Content by WIKIPEDIA articles! The object-relational impedance mismatch is a set of conceptual and technical difficulties that are often encountered when a relational database management system is being used by a program written in an object-oriented programming language or style; particularly when objects or class definitions are mapped in a straightforward way to database tables or relational schemata. This practice has been recommended and documented by some object-oriented literature as a way to use databases in object-oriented programs.