In this paper we employ the parsing and generation capabilities of DCG in Prolog to convert XML documents into object definitions to be stored in an object database. The system mainly consists of a DTD parser, a schema generator and a DI parser generator. The DTD parser is used to analyze the structure of DTD. The two generators take the parsing results of the DTD parser, and then produce database schema definitions and the DI parser. The database schema for a DTD is built by executing the generated schema definitions. The DI parser analyzes the document instance and produces the corresponding object definitions. The elements in the document are then stored in the object database by executing the object definition.