Semantic Keyword-based Search on Structured Data Sources First COST Action IC1302 International KEYSTONE Conference, IKC 2015, Coimbra, Portugal, September 8-9, 2015 : Revised Selected Papers - Cardoso, Jorge 1970-; Guerra, Francesco; Houben, Geert-Jan; Pinto, Alexandre Miguel; Velegrakis, Yannis (Lecture Notes in Computer Science, 2015)