Discovery of documents, data sources, facts, and opinions is at the very heart of digital information and knowledge services. Being able to search, discover, compile, and analyse relevant information for a user’s specific tasks is of utmost importance in science (e.g., computational life sciences, digital humanities, etc.), business (e.g., market and media analytics, customer relationship management, etc.) , and society at large (e.g., consumer information, traffic logistics, health discussions, etc.).