Development of the Japanese WordNet
Hitoshi ISAHARA, Francis BOND, Kiyotaka UCHIMOTO,
Masao UTIYAMA, Kyoko KANZAKI
National Institute of Information and Communications Technology
3-5 Hikari-dai, Seika-cho, Souraku-gun, Kyoto 619-0289 Japan
E-mail: {isahara, bond, uchimoto, mutiyama, kanzaki}@nict.go.jp

Abstract
After a long history of compilation of our own lexical resources, EDR Japanese/English Electronic Dictionary, and discussions withmajor players on development of various WordNets, Japanese National Institute of Information and Communications Technology started
developing the Japanese WordNet in 2006 and will publicly release the first version, which includes both the synset in Japanese and theannotated Japanese corpus of SemCor, in June 2008. As the first step in compiling the Japanese WordNet, we added Japanese equivalents
to synsets of the Princeton WordNet. Of course, we must also add some synsets which do not exist in the Princeton WordNet, and must
modify synsets in the Princeton WordNet, in order to make the hierarchical structure of Princeton synsets represent thesaurus-like
information found in the Japanese language, however, we will address these tasks in a future study. We then translated Englishsentences which are used in the SemCor annotation into Japanese and annotated them using our Japanese WordNet. This
article describes the overview of our project to compile Japanese WordNet and other resources which relate to our Japanese
WordNet.

1.

Introduction

After a long history of compilation of our own lexicalresources, EDR Japanese/English Electronic Dictionary,and discussions with major players on development ofvarious WordNets, we, Japanese National Institute ofInformation and Communications Technology (NICT),
started developing the Japanese WordNet in 2006 and will
publicly release the first version, which includes both thesynset in Japanese and the annotated Japanese corpus ofSemCor, in June 2008 just after the LREC2008
conference.
As the first step in compiling the Japanese WordNet, weadded Japanese equivalents to synsets of the Princeton
WordNet. Of course, we must also add some synsets
which do not exist in the Princeton WordNet, and must
modify synsets in the Princeton WordNet, in order to makethe hierarchical structure of Princeton synsets represent
thesaurus-like information found in the Japanese language,
however, we will address these tasks in a future study.
We then translated English sentences which are used in theSemCor annotation into Japanese and annotated themusing our Japanese WordNet1.
This article describes the overview of our project tocompile Japanese WordNet and other resources which
relate to our Japanese WordNet.

2.

Procedure

To develop and publicly release the Japanese WordNet, wemade a draft plan to compile the first version of ourJapanese WordNet in two years. We finished adding
Japanese word to ten thousand WordNet synsets as a1

We are thinking to annotate newly introduced gloss
annotation of WordNet with our Japanese WordNet.

foundation of Japanese WordNet in 2006 Japanese fiscal
year, and we are adding Japanese words to more synsets
and compiling other resources related to our Japanese
WordNet in 2007 Japanese fiscal year.
Stage 1 (2006)
As the first step of compiling the Japanese WordNet, wechose ten thousand synsets from the Princeton WordNet(WordNet 3.0) and add Japanese words to the synsets. To
choose the ten thousand synsets, we firstly used the core
synsets (4,959) of the WordNet. Then, we chose thosesynsets for which the total frequency of the words in thesynset is high.
In order to make the development efficient, weautomatically translate terms in existing WordNets, e.g.,
the Princeton English WordNet, French WordNet andSpanish WordNet into Japanese, by using electronic
dictionaries, such as EDR English-Japanese dictionary.
Our lexicographers are asked to choose proper Japanesewords for a synset from a set of Japanese equivalents ofterms in the synset, each of which has simple confidence
score based on the number of languages and/ordictionaries which output the equivalents.
We tried to translate all English terms in the synset(117,659) into Japanese and could find Japaneseequivalents for 62,832 synsets, among which we could
find equivalents for 3,391 core synsets. This means that we
could find candidate translations of terms in synsets by asimple dictionary lookup as shown in Table 1.
This was possible because terms in core synsets tend to begeneral terms and can be found in ordinary dictionaries.

All synsets in WN3.0
Core synsets
CBCCore + CBC

The number of synsets, for which
at least one Japanese equivalent
was found.
62,832
3,391
1,525
4,916

The total number of synsets.
117,659
3,434
1,526
4,960

Table 1. Dictionary lookup for Japanese equivalent

Another statistic we derived here is the semantic-concept
relation (Vossen, 2004) between original synsets and oursynsets. We checked the relations between terms in theoriginal synsets and our additional Japanese terms. Among
4,916 synsets, Japanese terms completely matched in
1,521 synsets and partially matched in 2,997 synsets.
Those synsets that did not completely match are thecandidates of modification to make the hierarchicalstructure of existing synsets represent thesaurus-like
information found in the Japanese language. We willconsider adding some new Japanese synsets to the originalsynsets for those synsets that did not completely match.
As for the number of candidates of Japanese equivalents
for all synsets, we obtained 215,630 Japanese terms as
equivalents of terms in original synsets. We classified
them into three types: equivalents obtained by more than
two authorities (type 1) such as dictionaries, by twoauthorities (type 2), and by only one authority (type 3). As
for type 1, among 16,620 terms, 9,042 terms (54%) arecorrect and used as Japanese terms in synsets. For type 2,among 26,268 terms, 13,986 terms (38%) are correct, andfor type 3, among 162,641 terms, 33,908 terms (20%) arecorrect. This shows that if we use as many authorities aspossible, the ratio of correct translations increases andtherefore the efficiency of compilation of Japanese
WordNet will be improved.
The actual procedure of assignment of equivalents is asfollows:
1.
2.
3.
4.

We examine the remarks, examples and synonyms in
the Princeton WordNet.
We consult an English-Japanese dictionary on themeanings of synonymous words.
We choose the Japanese equivalents which match theremarks in WordNet, by consulting a Japanese word
dictionary.
We decide semantic conceptual relations amongwords.

The form we are using during the process described above
is shown in Figure 1.
During the process of compiling the Japanese WordNet,
we encountered several interesting problems:Representation of different transcription in
Japanese. There are many orthographic variants inJapanese.
Differences in part-of-speech system between
Japanese and English, e.g., Japanese adjectives act

differently from English adjectives.
Differences of concept between Japanese andEnglish, e.g., some of the meanings of the Japaneseword “kioku (contents of memory, instrument ofmemory, action of memorization and so on)” matchthe meanings of “memory” in English, but others
do not.
Differences between concept structures in Japaneseand English, for which we should add
Japanese-peculiar synsets to the original wordnet.
We have finished developing the Japanese WordNet forten thousand synsets and moved to Stage 2.
Stage 2 (2007)
As the second step, we are enlarging the Japanese
WordNet and also are developing Japanese SemCor. As
for enlarging the Japanese WordNet, we will cover ten
thousand frequent words in the Juman dictionary and25,060 synsets (224,260 words) which appear in theMultiSemCor corpus.
We will translate all text in MultiSemCor into Japaneseand annotate them using our Japanese WordNet. We will
check all lexical gaps that we will encounter during
annotation of the Japanese SemCor.
We will complete all preparations for releasing theJapanese WordNet and Japanese annotated SemCor byJune 2008.

3.

Related Works

3.1 Previous researches
There are much work on building a Japanese WordNet.
Noun part – synsets and glosses – translated intoJapanese (Hayashi, 1999)
Some entries translated using context (Kaji &Watanabe, 2006)
Translation of (English) WordNet and EDR into RDF(Koide et al,. 2006)
But still no large-scale freely available Japanese WordNet

3.2 Ongoing related works
At NICT, we are conducting several researches
related/using Japanese WordNet (Bond et al., 2008;Kanzaki et al., 2008; Charoenporn et al., 2008).

We are one of the members of Kyoto Project (Vossen et al.,2008) at FP7 in EU.

4.

Future plan

We have four future plans for the development of Japanese
WordNet.
One plan is adding synsets which do not exist in thePrinceton WordNet, in order to make the hierarchicalstructure of Princeton synsets represent thesaurus-like
information peculiar to Japanese language.
Second plan is combining WordNet with other Japaneselexical resources via our Japanese WordNet. NICT holds
all copyrights of the EDR electronic dictionary which has
200 thousand words in Japanese and English and 400
thousand concepts constructed in a concept hierarchy. We
have already linked 981 synsets of WordNet 1.6 to EDR
concept entries. We will make this information available
to the public with our Japanese WordNet. We are alsoplanning to combine information in EDR with WordNet tocreate one big lexical resource with various kinds ofinformation such as Japanese words, their part-of-speech,
collocation information, and valence patterns. We are
currently developing Japanese-Chinese dictionary as anextension of EDR Japanese-English dictionary. Once it isfinished, we can also combine resources in Chinese with
WordNet via EDR dictionary.
The third plan is to develop WordNet for south-east Asian
languages. NICT has Thai Computational Linguistics
Laboratory (TCL) in Thailand which develops NLP
technology and resources in south-east Asia, such as Thai,
Indonesia and Malay. We have developed a tool forcollaboration named Knowledge Unifying Initiator (KUI)(Sornlertlamvanich, 2007) and started collaborative
development of WordNet for the languages in the region
using KUI as its platform.
The output of these activities will be publicly released inthe future.
The fourth plan is much more ambitious. NICT has
research groups on text processing, speech processing andimage processing at NICT’s Knowledge Creating
Communication Research Center in Kyoto. We arethinking to develop a huge real-world knowledge base and
our Japanese WordNet will be a core of this database.

5.

References

Bond, Francis et al., Bootstrapping a WordNet using
multiple existing WordNets., n Proceedings of the 6thInternational Conference on Language Resources andEvaluation (LREC 2008), 2008.
Charoenporn, Thatsanee et al. Semi-automatic
Compilation of Asian WordNet, In Proceedings ofAnnual Meeting of Japanese Society of NLP, 2008.
Hayashi Yoshihiko, Translating WordNet noun part into
Japanese for cross-language natural language
appreciations. In Technical Reports of SIG NLPNL130-10, 1999 (in Japanese)
Koide Seiji et al, OWL expressions on WordNet and EDR,
In AI society Semantic Web Ontology SIG13,
SIG-SWO-A601-03, 2006
Kaji Hiroyuki & Watanabe Mariko, Automaticconstruction of Japanese WordNet. In Proceedings ofthe 5th International Conference on Language
Resources and Evaluation (LREC 2006), 2006.
Kanzaki Kyoko et al., Extraction of Attribute Concepts
from Japanese Adjectives, In Proceedings of the 6thInternational Conference on Language Resources andEvaluation (LREC 2008), 2008.
Sornlertlamvanich, Virach et al., Collaborative Platform
for Multilingual Resource Development andIntercultural Communication, In: InterculturalCollaboration, Lecture Notes in Computer Science,
Volume 4568/2007, Springer, 2007.
Vossen, Piek. EuroWordNet: a multilingual database ofautonomous and language-specific wordnets connected
via an Inter-Lingual-Index, In: Special issue on
multilingual databases. International Journal ofLinguistics 17/2, 2004.
Vossen, Piek et al., KYOTO: A System for Mining,Structuring, and Distributing Knowledge AcrossLanguages and Cultures, In Proceedings of the 6thInternational Conference on Language Resources andEvaluation (LREC 2008), 2008.

Figure 1. Entry Form for Compilation of Japanese WordNet