(S (S (NP (NP (BASENP (NNP IBM) (POS 's)) (BASENP (NNP T.J.) (NNP Watson) (NNP Research) (NNP Center))) (PP (IN in) (BASENP (NNP Cambridge)))) (VP (VP (VP (VBD released) (BASENP (DT a) (JJ free) (NN tool))) (BASENP (NNP March) (NN 25))) (PP (IN for) (S (VP (VBG visualizing) (NP (NP (BASENP (DT the) (VBG changing) (NN history)) (PP (IN of) (NP (BASENP (DT a) (NN document)) (CC or) (NP (BASENP (NN directory)) (PP (IN of) (BASENP (NNS documents))))))) (COMMA ,) (VP (VBN called) (BASENP (NN history) (NN flow))))))))) (PERIOD .))