An electronic commerce system (10) includes a client computer (12) and a server computer (14). The client computer (12) is programmed to transmit to the server computer (14) an order acceptance request message (16) that includes a plurality of terms or conditions of a proposed offer for a purchase, including multiple options of at least one of the terms or conditions of the offer. The server computer (14) is programmed to process the order acceptance request (16) based on pre-programmed criteria and, based on the processing of the order acceptance request (16), to transmit to the client computer (12) an order acceptance response (18) that includes a plurality of amendments to the proposed offer. The processing of the order acceptance request (16) is performed by a controller module (22), and that initiates a plurality of calls to a plurality of plug-in modules (24 and 26) which use information in the databases (44) for formulating responses. The server (14) can handle fraud-avoidance and may initiate a call to a database of a virtual warehouse to ensure that a sufficient virtual inventory exists for the purchase.
