SOPA: Random Forests Regression for the Semantic Textual Similarity task

This paper describes the system used by the LIPN-IIMAS team in the Task 2, Semantic Textual Similarity, at SemEval 2015, in both the English and Spanish sub-tasks. We included some features based on alignment measures and we tested different learning models, in particular Random Forests, which proved the best among those used in our participation.