Research Directions on Big IoT Data Processing using Distributed Ledger Technology: A Position Paper Topics: Big Data fundamentals - Services Computing, Techniques, Recommendations and Frameworks; Data Processing ; Volume, Velocity, Variety and Veracity In Proceedings of the 4th International Conference on Internet of Things, Big Data and Security IoTBDS - Volume 1, 385-391, 2019 , Heraklion, Crete, Greece