ebXML (Electronic Business using extensible Markup language), sponsored by UN/CEFACT and OASIS, is a modular suite of specifications that enables enterprises of any size and in any geographical location to conduct business over the Internet. Using ebXML, companies now have a standard method to exchange business messages, conduct trading relationships, communicate data In common terms and define and resistor business processes. It is the mission of ebXML that provides an open XML-based infrastructure enabling the global use of electronic business information in an interoperable, secure and consistent manner by all parties for creating a single e1ectronic electronic market. This paper briefly overviews the concept of core component, context, assembly rule and context rule. Then, It designs by standard specifications of ebXML core component commonly used in an industry and among industries, and assembles business messages by using XML schema. Therefore, it suggests the mechanism which effectively exchanges business messages among the trading partners. This paper designs core component by using only three business messages of retail industry : orders, dispatch report, sales report.