1. An apparatus for defining a metadata schema to facilitate passing data between an eXtensible Markup Language (XML) document and a hierarchical database, the apparatus comprising: a storage device storing executable code; a processor executing the executable code, the executable code comprising: a database accessor accessing a database schema indicative of database field names and a hierarchical structure for a hierarchical database; a document accessor accessing a document schema that defines the hierarchical structure, content data syntax, and semantics of valid, well-formed, XML documents that can be passed into and out of the hierarchical database, the document schema comprising an XML element name that maps to a database field name in the database schema, the document schema comprising at least one directive metadata element not interfering with third-party applications using the document schema and facilitating passing data between the XML document and the hierarchical database; and an association module relating the database schema and the document schema to provide a metadata schema that enables data to be passed between an XML document and the hierarchical database.