Set Expander: A Knowledge-based System for Entity Set Expansion Topics: Applications, Research Projects and Web Intelligence; Data Web Mining; Knowledge Representation and Reasoning on the Web; Ontology Discovering, Modelling, Retrieving and the Semantic Web; Web Information Filtering and Retrieval; Web Programming; Web Services and Web Engineering In Proceedings of the 17th International Conference on Web Information Systems and Technologies WEBIST - Volume 1, 494-500, 2021