This document covers: Provision of a catalogue of fares Request for specific fare offers (including specific search criteria), Selection of one or several formal offers by the customer (pre-purchase), Initiation of the purchase, Commitment to buy, Reservation of a place on a specific journey, Reception of evidence of the purchase, Management after purchase (basic after-sale actions), All interactions that can be related to a persistent identity. These functions can be seen as the minimum required for the data flow of reservation from the travellers perspective. Though some of the studied APIs have functions beyond just reservation and involving other parties, the following activities are not in scope of this document nor the CoRoM project: Creation and distribution of the travel document, Travel planning, Payment interfaces with banking information systems, Validation of purchased access rights during travel, Control of purchased access rights during travel