An apparatus, system, and method are provided for passing data between an XML document and a hierarchical database. The apparatus, system, and method include a hierarchical database, a metadata schema, and a mapping module. The hierarchical database comprises a conventional hierarchical database, such as IMS. The metadata schema is derived from the hierarchical database. The metadata schema includes a first representation representative of the hierarchical structure of the hierarchical database, a second representation representative of the hierarchical structure of XML documents valid for passing into and out of the hierarchical database, one or more database field names, and one or more XML element names that map to the one or more database field names. The mapping module passes data between the XML document and the hierarchical database using the metadata schema.