12th International Workshop on Scalable Semantic Web Knowledge Base Systems (SSWS 2018) At the 147h International Semantic Web Conference (ISWC2018), Monterey, CA, USA October, 2018 SSWS 2018 PC Co-chairs’ Message SSWS 2018 is the twelfth edition of the successful Scalable Semantic Web Knowledge Base Sys- tems (SSWS) workshop series. The SSWS series is focused on addressing scalability issues with respect to the development and deployment of knowledge base systems on the Semantic Web. This 12th workshop aimed at providing a forum for discussing application-oriented issues of Semantic Technologies, with the focus on systems that turn large volumes of real-world data into actionable knowledge at industry domains. This goal imposed significant scalability requirements on storage and processing systems and demands for reliable workflows to curate and validate data from various sources. By inviting contributions that integrate methods and results from research on RDF and Property Graphs, this workshop brought together researchers and practitioners to share their ideas regarding building and evaluating scalable knowledge base systems for the web. In addition to the regular paper presentation sessions, this 12th SSWS workshop includes a poster session designed to facilitate sharing of ideas among researchers and practitioners. Further, this workshop arranges an industry talk by Amazon which now o↵ers Neptune, a fully managed graph database that supports both RDF and Property Graph data models. This year we received 9 submissions. Each paper was carefully evaluated by three workshop Program Committee members. Based on these reviews, we accepted 6 papers for presentation. Two of these papers where selected as best papers and are also published as part of the book “Emerging Topics in Semantic Technologies. ISWC 2018 Satellite Events. E. Demidova, A.J. Zaveri, E. Sim- perl (Eds.), ISBN: 978-3-89838-736-1, 2018, AKA Verlag Berlin”. These are the titles “Extending LargeRDFBench for Multi-Source Data at Scale for SPARQL Endpoint Federation” and “Assess- ing Linked Data Versioning Systems: The Semantic Publishing Versioning Benchmark” which are marked with an * in the table of contents. We sincerely thank the authors for all the submissions and are grateful for the excellent work by the Program Committee members. August 2018 Thorsten Liebig Achille Fokoue Zhe Wu Copyright c 2018 for the individual papers by the papers’ authors. Two papers are also published in ”Emerging Topics in Semantic Technologies. ISWC 2018 Satellite Events. E. Demidova, A.J. Zaveri, E. Simperl(Eds.), ISBN: 978-3-89838-736-1, 2018, AKA Verlag Berlin. Copying permitted for private and academic purposes. This volume is published and copyrighted by its editors. Program Committee Achille Fokoue Ralf Möller IBM Watson Research Center, USA Hamburg Univ. of Techn., Germany Raúl Garcı́a-Castro Raghava Mutharaju Univ. Politecnica de Madrid, Spain Wright State University, Ohio, USA Bernado Cuenca Grau Mariano Rodrı́guez-Muro University of Oxford, UK IBM Watson Research Center, USA Volker Haarslev Kavitha Srinivas Condordia University, Canada RivetLabs, USA Pavel Klinov Takahira Yamaguchi Complexible Inc., USA Keio University, Japan Adila A. Krisnadhi Zhe Wu Wright State University, Ohio, USA Oracle, USA Thorsten Liebig derivo GmbH, Germany Table of Contents The Fundamentals of Semantic Versioned Querying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Ruben Taelman, Hideaki Takeda, and Ruben Verborgh Stream Processing: The Matrix Revolutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Romana Pernischová, Florian Ruosch, Daniele Dell’Aglio, and Abraham Bernstein Extending LargeRDFBench for Multi-Source Data at Scale for SPARQL Endpoint Federation* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Hongyan Wu, Atsuko Yamaguchi, and Jin-Dong KimAli Hasnain, Muhammad Saleem, Axel-Cyrille Ngonga Ngomo, and Dietrich Rebholz-Schuhmann Assessing Linked Data Versioning Systems: The Semantic Publishing Versioning Benchmark* 45 Vassilis Papakonstantinou, Irini Fundulaki, and Giorgos Flouris Approximating Faceted Search for Graph Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Vidar Klungre, and Martin Giese Bridging Property Graphs and RDF for IoT Information Management . . . . . . . . . . . . . . . . . . . . 77 Abdullah Abbas, and Gilles Privat