SemEval-2015 Task 2: Semantic Textual Similarity

In semantic textual similarity, systems rate the degree of semantic equivalence between two text snippets.  One of the goals of the STS task is to create a unified framework for combining several semantic components that otherwise have historically tended to be evaluated independently and without characterization of impact on NLP applications. By providing such a framework, STS allows for an extrinsic evaluation of these modules. This edition three tasks were proposed: the English subtask, the Spanish subtask and the interpretable pilot subtask,  where systems needed to add an explanatory layer, that is, they had to align the chunks in the sentence pair, explicitly annotating the kind of relation and the score of the chunk pair.