Semantic Textual Similarity: past present and future Mona Diab author 2013-11 text Proceedings of the Joint Symposium on Semantic Processing. Textual Inference and Structures in Corpora Octavian Popescu editor Alberto Lavelli editor Trento, Italy conference publication diab-2013-semantic https://aclanthology.org/W13-3806/ 2013-11 6