  The lack of interoperability among IoT platforms has led to a fragmented
environment, where the users and society as a whole suffer from lock-ins, lack
of privacy, and reduced functionality. This paper presents SOFIE, a solution
for federating the existing IoT platforms in an open and secure manner using
Distributed Ledger Technologies (DLTs) and without requiring modifications to
the IoT platforms, and describes how SOFIE is used to enable two complex real
life pilots: food supply chain tracking from field to fork and electricity
distribution grid balancing with guided electrical vehicle (EV) charging.
SOFIE's main contribution is to provide interoperability between IoT systems
while also enabling new functionality and business models.
