A term not well defined but applied to software products that provide persistence for applications written in object-oriented languages with features such as rollback and recovery. Thus ONTOS provides persistence for C++ and GemStone for a variant of Smalltalk-80. There is no generally accepted object-oriented data model on which products can be based as with the relational model, although various proposals have been and are being made. It remains unclear whether all the concepts of object-oriented programming are relevant in the database context.