As a result , a text to text similarity measure is built based on word to word similarity . It is as-sumed that combining word to word similarity metrics to text level would be a good indicator of text to text similarity . 4 Sagan for MT evaluation Sagan for MT evaluation is based on a core devel-opment to approach the Semantic Textual Similari-ty task ( STS ) . The pilot task STS was recently defined in Semeval 2012 ( Aguirre et al , 2012 ) and has as main objective measuring the degree of semantic equivalence between two text fragments .