Methods and apparatus, including computer program products, implementing and using techniques for providing a discovery service that provides a mapping from an electronic product code to electronic product code information services that include information about an item represented by an electronic product code. The discovery service includes a database containing a list of custodians for the item and a service interface through which electronic product code information services and applications can access the entries in the list. The list includes an entry for each custodian. Each entry includes the electronic product code number, a pointer to an electronic product code information service associated with the custodian, and a trip identifier for the item. The service interface includes several services enabling traceability of the item represented by the electronic product code. Methods and apparatus, including computer program products for using a trip identifier in a discovery service are also described.