Semantic Systems. The Power of AI and Knowledge Graphs : 15th International Conference SEMANTiCS 2019 Karlsruhe Germany September 9–12 2019 Proceedings Web Semantics and Linked (Open) Data Machine Learning and Deep Learning Techniques Semantic Information Management and Knowledge Integration Terminology Thesaurus and Ontology Management Data Mining and Knowledge Discovery Semantics in Blockchain and Distributed Ledger Technologies This open access book constitutes the refereed proceedings of the 15th International Conference on Semantic Systems SEMANTiCS 2019 held in Karlsruhe Germany in September 2019. The 20 full papers and 8 short papers presented in this volume were carefully reviewed and selected from 88 submissions. They cover topics such as: web semantics and linked (open) data; machine learning and deep learning techniques; semantic information management and knowledge integration; terminology thesaurus and ontology management; data mining and knowledge discovery; semantics in blockchain and distributed ledger technologies