Copyright © 2019 Shohei Tanaka All Rights Reserved (4)NCM → Copyright © 2019 Shohei Tanaka All Rights Reserved 4/37 (5)e.g

(1)

1 2 2

(2)

2^/37

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Neural Conversational Model (NCM)

NCM [Vinyals et al., 2015]

?

3^/37

RNN

<sos>

<eos>

(4)

NCM

→

(5)

e.g.

Why-QA [Oh et al., 2013]

2

(6)

→

(7)

7^/37

(8)

1. 2.

3.

1. 2.

3.

NCM

e.g.

1

2

(9)

1. 2.

3.

NCM 1

(10)

1. 2.

3.

1. 2.

3.

NCM

(e.g.

) 1

2

→

(11)

-

(12)

(

e ( (

( ()W (

(e.g.

→ b)

(13)

→ →

( )

…

( )

… …

( )

… …

(14)

Role Factored Tensor Model (RFTM) [Weber et al., 2018]

+ …

W₁

…

1

T

W₂

…

2

T

(15)

15^/37

(16)

NCM EncDec, HRED

1-best ( ),

/

260 Twitter

( 6 )

(17)

attention )

Attention Encoder, Decoder (

hidden state vector

Encoder-Decoder with Attention [Luong et al., 2015]

(18)

Hierarchical Recurrent Encoder-Decoder [Serban et al., 2016]

(hierarchical) utterance encoder

context encoder

Context Encoder Utterance Encoder

(19)

NCM EncDec HRED EncDec HRED

12 % 70 %

(20)

• BLEU

N-gram

• NIST

BLEU

(21)

• Vector Extrema

( e_s

e_w d ₎

(22)

BLEU, NIST, and extrema

NCM

NCM BLEU NIST extrema

EncDec

1-best

HRED

1-best

(23)

• Dist-1, 2

N-gram

• Pointwise Mutual Information (PMI)

Dist, PMI

(24)

Dist and Pointwise Mutual Information (PMI)

NCM dist-1 dist-2 PMI

EncDec

1-best

HRED

1-best

(25)

NCM

v.s.

HRED

HRED + /

(26)

2 2 2 2

• Word coherency

0 2 1 3 1

• Dialogue continuity

0 2 1

2 2

• 2

• 1

(27)

Word Coherency

28.62 37.47 33.91

0% 20% 40% 60% 80% 100%

Coherency

1-best neither Re-ranking w/o embedding

30.10 44.50 25.40

0% 20% 40% 60% 80% 100%

Coherency

1-best neither Re-ranking w/ embedding

(28)

Dialogue Continuity

40.84 20.63 38.53

0% 20% 40% 60% 80% 100%

Continuity

1-best neither Re-ranking w/o embedding

35.50 26.30 38.20

0% 20% 40% 60% 80% 100%

Continuity

1-best neither Re-ranking w/ embedding

(29)

• Word coherency

• Dialogue continuity

(dist) (PMI)

(30)

30^/37

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(

5 %

% %5 +) +

5 % % 0

/ ( )

26 19 51

(

26 + 19

= 45

(32)

02 2 )5 5

5 % ) 02 2

(

/ ( ) ( )

8 14

4 90

5

8 + 14

= 22

(33)

1

1 (1-best)

(Re-ranked) 1

(34)

2

… (1-best)

(Re-ranked)

(35)

3 )

( ) … … …

(1-best) (

(Re-ranked) (

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36^/37

(37)

/

3 3 7

•