3 PROBABILISTIC TOPIC MODELSIMLDA2(DI, DJ) = 10W(ˆΘ(DI),Θˆ(DJ))CELIK...

3.3 Probabilistic Topic Model

sim

LDA2

(D

i

, D

j

) = 10

W

θ

(

Di

)

,

θ

ˆ

(

Dj

)

)

Celikyilmaz et al. (2010) presented probabilistic

topic model based methods to measure the similar-

where θ ˆ

(D

i

)

is document D

i

’s probability distribu-

ity between question and candidate answers. The

candidate answers were ranked based on the hidden

tion of topics as defined earlier.

4 Information Need Prediction using

P r(f, a|e). For different alignment models differ-

Statistical Machine Translation Model

ent approaches were proposed to estimate the cor-

responding alignments and parameters. The detail-

There are two reasons that we need to predict in-

s can be found in (Och et al., 2003; Brown et al.,

formation need. It is often the case that the query