A system may provide generation of a file to declare one or more persistent classes, the file formatted according to a markup language syntax, and generation, based on the file, of code of an object-oriented language to declare the one or more persistent classes and to describe a structure of each of the one or more persistent classes. Further aspects may include calling a constructor to register an interface to a description of a persistent class, accessing the registered interface to determine the structure of the persistent class, and processing an instance of the persistent class based on the determined structure.