“In database research, the big data issue has mainly been addressed as a scale issue: storing and providing the same level of services as before in terms of speed, reliability, interoperability and distribution.The scale challenges are now being solved by research and industry. A less advertised issue raised by the increase of available data is the unprecedented opportunity for discoveries and exploratory studies. For example, Metagenomics is a research ???eld in Biology that sequences DNA from random samples of material collected in the wild to discover the largest possible diversity of living species. With new high-throughput sequencing technologies, the genome of millions of species are sequenced and stored in databases but are not systematically explored due to the lack of appropriate tools. Bank transactions are being logged and monitored to ???nd patterns of frauds, but new schemes arise continually that need to be discovered in the billions of transactions logged daily. This task of discovery of innovative fraud schemes is not well supported by existing tools either. Similar problems arise in a wide range of domains where data is available but requires speci???c exploration tools, including sentiment analysis on the Web, quality control in Wikipedia, and epidemiology to name a few. However, current database technologies do not meet the requirements needed to interactively explore massive or even reasonably-sized data sets”