Front Matter, Table of Contents, Foreword, Conference Organization, External Reviewers, Authors. In Peter Müller, editor, 31st European Conference on Object-Oriented Programming, ECOOP 2017, June 19-23, 2017, Barcelona, Spain. Volume 74 of LIPIcs, Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik, 2017. [doi]