THE PDES/STEP SPECIFICATIONS ALLOW ENGINEERING APPLICATIONS TO EXCHANGE INFORMATION ABOUT PRODUCTS. UNLIKE PREVIOUS SPECIFICATIONS FOR ENGINEERING INFORMATION, THESE SPECIFICATIONS CONTAIN A DATA DEFINITION LANGUAGE CALLED EXPRESS THAT CAN BE USED TO DESCRIBE ANY TYPE OF ENGINEERING DATA. APPLICATIONS THAT WANT TO EXCHANGE DATA USING PDES/STEP CAN DO SO BY WRITING SPECIFIC SOFTWARE TO PROCESS ONE PDES/STEP MODEL FOR ONE TYPE OF PRODUCT, OR THEY CAN WRITE GENERIC SOFTWARE TO PROCESS THE EXPRESS DESCRIPTION OF ANY PDES/STEP MODEL FOR ANY TYPE OF PRODUCT. THIS PAPER DESCRIBES HOW OBJECT-ORIENTED TECHNOLOGY CAN IMPLEMENT THE LATTER CASE.