Due to a lack of shared practices of deployment, installation and application, the first commercial smart ticketing projects were built on proprietary specifications limiting their scope of integration and compatibility between them. As a result, a move towards global standards and specifications can be observed in current research as well as in practical applications. Therefore, interoperability in public mass transit has become a central aspect of e-ticketing. In this paper, we develop a standardised process on how to handle the emerging smart card data in an interoperable environment. The goal is to present a unified approach where data mining tools and model applications can be tested and implemented in every region embedded in the integrated network. The Interoperable Smart Card Data Chain (ISCDC), which is presented in this paper, provides a continuous procedure for standardised data handling and management. Using insights from expert interviews with German public transit entities, we deduce best practices on how to implement the ISCDC effectively.