From Group-by to Accumulation: Data Aggregation Revisited Topics: Big Data fundamentals - Services Computing, Techniques, Recommendations and Frameworks; Software Frameworks (MapReduce, Spark etc) and Simulations; SQL/NoSQL databases, Data Processing Techniques, Visualization and Modern Technologies In Proceedings of the 2nd International Conference on Internet of Things, Big Data and Security IoTBDS - Volume 1, 370-379, 2017 , Porto, Portugal