Score S S = ∑ ∑ = + = + = M i j i ij M i ij s s W s W S Score 0 ' 1 1 ) | ( ) ( ) ( β α εςʔτ Sij ͷॏΈ ɾ tf ɾ idf Sij ͱ Si+1j’ ͷϦϯΫͷॏΈ ɾ୯ޠτϥΠάϥϜ֬ ˠ ୯ޠόΠάϥϜ֬ ɾΓड͚֬ ) 1 ' 1 ( + + − ≤ ≤ + i M N j i
200 z ςετσʔλ ˰ 200 z ϦϑΝϨϯεͷݸ ˰ 5 ݸ z ཁฏۉ(আ) ˰ 0.59ʢ0.41ʣ z ༏ઌֶशͰ10ׂަࠩݕఆ z ධՁࢦඪ z BLEUείΞɼROUGEείΞ(maxROUGE) ςετσʔλ ೖྗܗଶૉฏۉ 42.8 ϦϑΝϨϯεܗଶૉฏۉ 25.3
c, )( ( ngram Count Ref Max ngram Count ngram Count clip = R ∑ ∑ ∑ = = = ' 4 1 ) ' ( ) c, )( ( ) log 1 exp( ) , BLEU(c ngram ngram clip n n n ngram Count ngram Count p p n BP R R ɾ
channel modelΛܭࢉ ۟ߏΛ༻͍͍ͯΔͨΊຊޠʹରԠͤ͞Δͷࠔ z ኍౢΒ[05] ϔουϥΠϯੜʢ୯ޠநग़ʣ noisy channel model ͷ channel model ʹ ̨̢̫Λͬͨ୯ޠॏཁʢ͜ͷϔουϥΠϯʹඞཁͳ୯ޠ બΛSVMΛͬͯߦ͏ͷ͍͠ͷͰʁʢจ຺ґଘʣʣ
i x x y ܇࿅σʔλ > 1 i x 1 + = i y 2 i x ˠ < 1 i x 2 i x 1 − = i y ˠ ૉੑϕΫτϧx͕༩͑ΒΕͨͱ͖ͷ༏ઌG(x) ∑ − = ij ij i ij i y G )) ( ) ( ) ( ) ( ( ) ( 1 x h x h x h x h x ɾ ɾ α
etc. z ύϥϝʔλΛௐ ˰ upper Λݟͨͱ͖ʹ࠷ߴ͔ͬͨई ) , unigram( ) ( ) ( 1 x x x h x h ij ij λ = ɾ ) , posbigram( ) , trigram( ) , ( skipbigram 4 3 2 x x x x x x ij ij ij d λ λ λ + + +
( ) ( ) ( ' ' 1 ' 1 ' 1 j i ij j i ij j i s s W s W s s + + + + + = β α φ φ j i <s> n1 n2 n3 n4 n5 n6 n7 n8 n10 n9 </s> ೖྗจ <s> m2 m1 m3 m4 m5 </s> ॖจʢग़ྗจʣ