This book constitutes the thoroughly refereedpost-conference proceedings of the First COST Action IC1302 InternationalKEYSTONE Conference on semantic Keyword-based Search on Structured Data Sources,IKC 2015, held in Coimbra, Portugal, in September 2015.The 13 revised full papers, 3 revised short papers, and 2 invited papers werecarefully reviewed and selected from 22 initial submissions. The paper topicscover techniques for keyword search, semantic data management, social Web andsocial media, information retrieval, benchmarking for search on big data.