Workshop and Poster Proceedings of the 8th Joint International Semantic Technology Conference (JIST 2018) November 26-28, 2018 Awaji City, Hyogo, Japan Preface The Joint International Workshop on PAOS 2018 and PASSCR 2018 is co-located with the 8th Joint International Semantic Technology Conference (JIST 2018). The Fifth International Workshop on Practical Application of Ontology for Semantic Data Engineering (PAOS2018) focuses on three related themes: Ontology Design and Modelling, Ontology Application for Enhancing Linked Data Publishing, and Ontology Application for Enhancing Linked Data Consumption. The 3rd International Workshop on Platforms and Applications for Social problem Solving and Collective Reasoning (PASSCR2018) focuses on integrating state-of-the-art techniques and platforms to enhance and accommodate social intelligence to solve various social issues. This year, both workshops were jointly organized, and seven submissions were selected and are included in the proceedings. Each submission was reviewed by at least two program committee members. The Poster and Demonstration track was held in conjunction with the JIST 2018 conference. The aim of the Poster and Demonstration track was to provide an opportunity for poster presenters to present late-breaking research results, ongoing research projects, and speculative or innovative work in progress. It also provides an interactive setting for the accepted papers of the main track to present and to receive direct feedback from audience and to demonstrate a supporting prototype implementation. Each submission for the Poster and Demonstration track was reviewed by at least two program committee members. In total, fourteen submissions were selected and are included in the proceedings. We would like to thank the program committee members, and JIST 2018 organizers for their effort to make this happen. Rathachai Chawuthai (PAOS2018 and PASSCR2018 co-chair) Seiji Koide (PAOS2018 and PASSCR2018 co-chair) Naoki Fukuta (PAOS2018 and PASSCR2018 co-chair) Takeshi Morita (PAOS2018 and PASSCR2018 co-chair) Hanmin Jung (Poster and Demo track co-chair) Shinichi Nagano (Poster and Demo track co-chair)