In order to achieve interoperability between diverse types of computer systems for the purpose of e-commerce, a system and method are provided for retrieving data from multiple relational databases into an XEDI document. First, a DTDSA is used to create an intermediate format for the data. Then, an annotated interoperable (universal) DTD is used to create the XEDI document. For depositing data from an XEDI document into multiple relational databases, a reverse process is used. The universal DTD is used to create the intermediate format. Then the DTDSA is used to create the relational database format. The deposit process requires analysis of join unions of data sought to be deposited, and also a static reversibility check for the DTDSA. A GUI interface is provided for generating annotations.