This book constitutes the thoroughly refereed post conference proceedings of the 4th edition of the Semantic Web Evaluation Challenge, Sem Web Eval 2017, co-located with the 14th European Semantic Web conference, held in Portoroz, Slovenia, in May/June 2017.This book includes the descriptions of all methods and tools that competed at Sem Web Eval 2017, together with a detailed description of the tasks, evaluation procedures and datasets. The 11 revised full papers presented in this volume were carefully reviewed and selected from 21 submissions. The contributions are grouped in the areas: the mighty storage challenge; open knowledge extraction challenge; question answering over linked data challenge; semantic sentiment analysis.