This part of ISO 24014 provides the basis for the development of multi-operator/multi-service Interoperable public surface (including subways) transport Fare Management Systems (IFMSs) on a national and international level.This part of ISO 24014 is applicable to bodies in public transport and related services which agree that their systems need to interoperate.While this part of ISO 24014 does not imply that existing interoperable fare management systems need to be changed, it applies so far as it is practically possible to extensions of these.This part of ISO 24014 covers the definition of a conceptual framework which is independent of organisational and physical implementation. Any reference within this part of ISO 24014 to organisational or physical implementation is purely informative.The objective of this part of ISO 24014 is to define a reference functional architecture for IFMSs and to identify the requirements that are relevant to ensure interoperability between several actors in the context of the use of electronic tickets.