Roaming in the context of this part of ISO/TS 17575 is understood as the ability of a Front End to operate in more than one EFC context either consecutively or at the same time. Data elements required defining operational properties of a single EFC context are defined in ISO/TS 17575‑3. The additional data elements required providing interoperability in overlapping and/or interdependent EFC contexts are defined in this part of ISO/TS 17575.