Kai Sauerwald, Matthias Thimm: Proceedings of the 21st International Workshop on Non-Monotonic Reasoning co-located with the 20th International Conference on Principles of Knowledge Representation and Reasoning (KR 2023) and co-located with the 36th International Workshop on Description Logics (DL 2023), Rhodes, Greece, September 2-4, 2023. CEUR Workshop Proceedings 3464, CEUR-WS.org 2023