This paper discusses the representation of coordinate structures in the Universal Dependencies framework for two head-final languages, Japanese and Korean. UD applies a strict principle that makes the head of coordination the left-most conjunct. However, the guideline may produce syntactic trees which are difficult to accept in head-final languages. This paper describes the status in the current Japanese and Korean corpora and proposes alternative designs suitable for these languages.

1. Coordinate Structures
in Universal Dependencies
for Head-final Languages
Hiroshi Kanayama IBM Research
Masayuki Asahara NINJAL, Japan
Yusuke Miyao University of Tokyo
Yuji Matsumoto NAIST
1
Na-Rae Han University of Pittsburgh
Jena D. Hwang IHMC
Jinho Choi Emory University
UD Workshop 2018
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages

2. UD has a universal principle of
left-headed coordinate structures
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 2
John
PROPN
and
CCONJ
Mary
PROPN
conj
cc
she
PRON
love
VERB
nsubj obj
Parallel
He
PRON
and
CCONJ
or
CCONJ
hate
VERB
conj
cc
conj
cc
root
Parallel Parallel
It’s reasonable as long as conjuncts are “parallel”
en

3. In head-final languages, all of content word
dependencies are right-headed
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 3
た
-PAST
AUX
妻
‘wife’
NOUN
が
-NOM
ADP
友達
‘friend’
NOUN
鞄
‘bag’
NOUN
を
-ACC
ADP
に
-DAT
ADP
見せる
‘show’
VERB
nsubj
case
買っ
‘buy’
VERB
aux case case
acl obj
obl
아네가
‘wife’
NOUN
산
‘buy’-PAST
VERB
가방을
‘bag’-ACC
NOUN
친구에게
‘friend’-DAT
NOUN
보이다
‘show’
VERB
nsubj acl obj obl
மனைவி
‘wife’
NOUN
வாங்கிய
‘buy’-PAST
VERB
னைனய
‘bag’-ACC
NOUN
நண்ைரிடம்
‘friend’-DAT
NOUN
காட்டுகிறேன்
‘show’
VERB
nsubj acl obj obl
ja
ko
ta
。
.
PUNCT
.
.
PUNCT
.
.
PUNCT
punct
punct
punct

4. Left-headed nominal coordination produces
terrible structures in Japanese
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 4
が
-NOM
ADP
犬
‘dog’
NOUN
と
-AND
ADP
走る
‘run’
VERB
猫
‘cat’
NOUN
case
nsubj
ja
が
-NOM
ADP
犬
‘dog’
NOUN
と
-AND
CCONJ
走る
‘run’
VERB
猫
‘cat’
NOUN
conj
cc
nsubj
case
dog and cat
long distance
case marker
Non-syntactic
dependency
Breaking
head-finalness

5. Left-headed verbal coordination produces
terrible structures in Korean
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 5
붉고
‘red’
ADJ
공
‘ball’
NOUN
큰
‘big’
ADJ
acl
conj
acl
red and big
Breaking
head-finalness
붉고
‘red’
ADJ
공
‘ball’
NOUN
큰
‘big’
ADJ
A form to
modify a NOUN
A form to modify
a VERB/ADJ
ko

6. Imagine a notorious (but rare) case in English:
we are always suffered from this
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 6
Long distance
markingen
John
PROPN
and
CCONJ
Mary
PROPN
’s
PART
conj
cc
case
John
PROPN
and
CCONJ
Mary
PROPN
’s
PART
conj
cc
case
Covers only
right conjunct
Inconsistent annotations
in UD English-EWT
Inconsistent annotations
in UD English-EWT
Right-headed coordination solves this case, and many of cases in head-final languages

7. Completely different structures
for slightly different interpretations
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 7
て
-ADV
CCONJ
走る
‘run’
VERB
笑っ
‘laugh’
VERB
“笑って走る”
て
-ADV
SCONJ
走る
‘run’
VERB
笑っ
‘laugh’
VERB
conj
cc
advcl
mark
“laugh and run”
 coordination (left-headed)
“run with laughing”
 subordination (right-headed)
ja
No clear boundary between coordination and subordination  risk of annotation catastrophe

8. Problems in handling coordination are
losing universalness of UD
Current UD Japanese:
 conj is never used, regarding there is no pure coordination
 Right-head nmod/advcl for nominal/verbal modification
Current UD Korean:
 Left-head coordination in UD Korean-GSD
 Right-head coordination in UD Korean-KAIST (non-official distribution)
 New proposal for right-head [Noh+ 2018 (this workshop)]
 Cannot enjoy cross-lingual transfer learning
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 8

9. Right-headed coordination is easy to learn
for Japanese and Korean UDPipe
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 9
A Band
A Band
conversion
Japanese - GSD
UAS / LAS
Korean - GSD
UAS / LAS
Left-
headed
73.6 71.8 69.5 61.2
Right-
headed
76.7 74.0 77.2 65.0

10. We propose to modify UD guidelines
to add flexibility of coordination orientation
Right-headed coordination structures are much more suitable for
head-final languages
• Intuitiveness, linguistic soundness
• consistent annotations
• cross-lingual consistency for transfer learning
• Higher learnability (3 to 4 points higher in UDPipe)
2018/11/1 UDW2018: Coordinate Structures in Head-final Languages 10
A Band