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; Guerra, Francesco; Houben, Geert-Jan; Pinto, Alexandre Miguel; Velegrakis, Yannis (Springer International Publishing : Imprint: Springer, 2015)