Several approaches for this step have been proposed such as the longest common substring (Agichtein et al., 2001), substrings in suffix trees (Ravichandran and Hovy, 2002;Ruiz-Casado et al., 2007) and edit distance based alignment (Ruiz-Casado et al., 2007).
finally, unlike other approaches, the Espresso approach only considers the relationships between the targets and the patterns.