DeepOntoNLP & X-SENTIMENT 2021, Advances in Semantics and Explainability for NLP: joint proceedings of the DeepOntoNLP and X-SENTIMENT workshops : joint proceedings of the 2nd International Workshop on Deep Learning Meets Ontologies and Natural Language Processing (DeepOntoNLP 2021) & 6th International Workshop on Explainable Sentiment Mining and Emotion Detection (X-SENTIMENT 2021), co-located with co-located with 18th Extended Semantic Web Conference 2021 : Hersonissos, Greece, June 6th-7th, 2021 (moved online)