With the ever-growing amount of data produced by humans as well as IoT devices and smart environments, there is a strong need for tools and natural user interfaces to explore and analyse these large datasets forming part of the Big Data era. There has been a lot of research on how to efficiently batch process large datasets and create some static reports for the analysis of the underlying dataset, but recently there is an increasing interest in real-time processing and query adaptation in Big Data environments, enabling so-called human-in-the-loop data exploration.