予め組込まれている類似度

WT_SMARTWA ::=
        avelen = DF(w) / Nr(w),
        slope = .2,
        norm = (avelen + slope * (DF(.|d) - avelen)) * (1 + log(TF(.|d) / DF(.|d))),
        1 / norm \sum_t (1 + log(TF(t|d))) * weight(t|q) .

WT_SMARTAW ::=
        log1p(Nr(w) / DF(.|d)) / DF(.|q) \sum_t (1 + log(TF(t|d))) / (1 + log(TF(.|t) / DF(.|t))) .

WT_SMART ::=
        aveTFq = TF(.|q) / DF(.|q),
        avelen = DF(w) / Nr(w),
        slope = .2,
        norm = (avelen + slope * (DF(.|d) - avelen)) * (1 + log(TF(.|d) / DF(.|d))),
        1 / norm \sum_t (1 + log(TF(t|q))) / (1 + log(aveTFq)) * idf(t) * (1 + log(TF(t|d))) .

WT_OKAPI_BM2 ::=
        k1 = 2,
        b = .75,
        avgdl = DF(w) / Nr(w),
        tfd = TF(.|d),
        \sum_t log((Nr(w) - DF(t) + 0.5) / (DF(t) + 0.5)) * (TF(t|d) * (k1 + 1)) / (TF(t|d) + k1 * (1 - b + b * TF(.|d) / avgdl)) .

WT_COSINE ::= cosine(d, q) .

WT_COSINE_TFIDF ::=
WT_DOT_PRODUCT ::=
WT_DOT_PRODUCT_TFIDF ::=