The EU-funded HACID project is developing a hybrid collective intelligence based on the synergy between humans and machines to find solutions to real-world open-ended problems. The solutions to these problems are not constrained to a limited set of alternatives, and span many knowledge domains. HACID will explore a new approach that brings together human experts and AI-supported knowledge representation to create new tools for decision making. Two case studies will be considered. The first one will address knowledge fragmentation in medicine, helping medical professionals make more accurate diagnoses. The second one will provide support to policy makers in defining urban adaptation strategies to face future impacts of climate change.