Proceedings of the ECML/PKDD 2015 Discovery Challenges co- located with European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases (ECML-PKDD 2015) ECML-PKDD 2015 discovery challenges: http://www.ecmlpkdd2015.org/discovery-challenges CEUR-WS proceedings online: http://ceur-ws.org/Vol-1526