Methods and apparatus for disseminating over the Internet product information produced and maintained by product manufacturers using existing universal product codes (bar codes) as access keys. A cross-referencing resource preferably implemented by the existing Internet Domain Name System (DNS) receives Internet request messages containing all or part of a universal product code value and returns the Internet address at which data or services relating to the identified product, or to the manufacturer of that product, may be obtained. By using preferred Web data storage formats and protocol which conform to XML, XLS, XLink, Xpointer, RDF and Web service standards specifications, product and company information may be seamlessly identified, retrieved and integrated with information from other sources. A "web register" module can be employed to provide an Internet interface between a shared sales Internet server and an otherwise conventional inventory control system, and operates in conjunction with the cross-referencing server to provide detailed product information to Internet shoppers who may purchase goods from existing stores via the Internet.