English Adverb Generation 
in Japanese to English Machine Translation 
Kentaro OGURA, Francis BOND and Satoru IKEHARA 
NTT Communication Science Laboratories 
1-2356 Take, Yokosuka-shi, Kanagawa-ken, 238-03 JAPAN 
{ogura, bond, ±kehara}@nttkb. ntt. jp 
Abstract 
This paper proposes an English adverb 
ordering method based on adverb gram- 
matical functions (subjuncts, adjuncts, dis- 
juncts and conjuncts) and meanings (pro- 
cess, space, time etc.), preferred positions 
in sentences (initial, medial, end, pre, 
post), and priorities between adverbs with 
the same preferred position. 
1 Introduction 
Adverbs I have various complex grammatical func- 
tions in sentences but they do not construct the main 
parts of sentence meaning. In natural language pro- 
cessing, therefore, the study of adverbs has not de- 
veloped very far to date. 
Linguists have examined adverb grammatical 
functions and meanings in detail(Quirk et al., 
1985) (Greenbaum, 1969). Our method is based on 
these studies about adverb grammatical functions 
and meanings. Other adverb studies by linguists in- 
clude studies which handle the meanings of specific 
adverbs, such as "even ", "s~ill" and "already " and 
temporal adverb studies which handle temporal se- 
mantics in sentences. 
The main problems in adverb processing in 
Japanese to English machine translation(Ogura et 
al., 1993) are as follows: 
1. the multiplicity of adverb meanings 
2. differences in expression between Japanese and En- 
glish for adverbial meaning 
3. word ordering of English adverbs in English gener- 
ation 
4. representation of adverbs in a computer 
In this paper, we focus our attention on the 3rd 
problem. 
2 Classification of English Adverbs 
2.1 Position 
In our adverb position system for English adverb 
generation, 5 positions are provided. The first is 
initial position (IP), the beginning of the sentence. 
The second is medial position (MP), between the 
subject and predicate, or if auxiliary verbs are in- 
volved in the sentence just after the first auxiliary 
1In this paper, adverbs include idiomatic adverbial 
phrase, such as "on purpose". 
verb. The third is end position (EP), after a predi- 
cate. Pre position (PreP) and post position (PostP) 
are provided for adverbs as modifiers. A pre posi- 
tion adverb comes before a modificant and a post 
position adverb comes after a modificant. 
2.2 Classification 
Adverbs can roughly be divided into subjuncts, ad- 
juncts, disjuncts and conjuncts by their grammatical 
function. We classify adverbs by specifying differ- 
ences in meaning and preferred positions within sen- 
tences for each adverb. The classification is shown 
in Figure 1. 
Subjuncts 
Viewpoint, Courtesy, 
Subject-orientation Item General 
Volitional MP & EP 
Focusing Restrictive PreP & PostP, 
Additive PreP & PostP & EP & IP & MP, 
Emphasizers Prep & EP, 
Amplifiers PreP & PostP & EP, 
Downtoners PreP & EP, 
Adjuncts 
Manner, Means, Instrument, Position, Direction, 
Time-position MP & EP, 
Span MP & EP, 
Time-frequency Definite, 
Indefinite MP & EP 
Disjuncts 
Style, 
Content Value Judgment Non-subject, 
Subject, 
Degree of truth 
Conjuncts IP & EP 
Post Position Numeral Modifiers 
Figure 1: Adverb Classification 
3 Word Ordering Method for 
English Adverbs 
Adverbs usually have many meanings, especially ad- 
verbs which are used frequently in our daily life. 
Normally the difference in meaning is indicated by 
the position in the sentence. 
The position of an adverb depends not only on 
the adverb's meaning but also on the relationship 
between the adverb and other sentence elements. 
Figure 2 shows order priorities in adverb position, 
for when two or more adverbs come in the same posi- 
tion. ~ shows the priority at some position, the left 
190 
side of the right arrow comes before the right side of 
the right arrow in the sentence. The priority reflects 
the scopes of adverbs. For example, conjuncts usu- 
ally have wider scope than disjuncts, so conjuncts 
come before disjuncts at the initial position. 
Initial position 
Conjuncts =~ 
Style Disjuncts, Content Disjunets =~ 
Viewpoint Subjuncts, 
General Subject-orientation Item Subjuncts =~ 
Additive Focusing Subjuncts 
Medial position 
Indefinite Time-frequency Adjuncts =~ 
Time-position Adjuncts =~ 
Span Adjuncts =~ 
Volitional Subject-orientation Item Subjuncts, 
Courtesy Subjuncts =~ 
Additive Focusing Subjuncts 
End position 
Amplifiers, Downtoners =* 
Manner & Means & Instrument Adjuncts 
Direction Adjuncts =~ 
Position Adjuncts =,, 
Span Adjuncts =V 
Definite Time-frequency Adjuncts, 
Indefinite Time-frequency Adjuncts =~ 
Time-position Adjuncts ::~ 
Volitional Subject-orientation Item Subjuncts =~ 
Emphasizers =V 
Additive Focusing Subjuncts 
Conjuncts 
Figure 2: Word Order of Adverbs 
4 Experimental Results 
4.1 Experiment 1 
The first experiment is performed on sentences with 
at least one Japanese adverb taken from the "Dictio- 
nary of Basic Japanese Usage for Foreigners". The 
sentences are translated by a human translator. We 
manually examined whether English adverbs in the 
translation would be generated correctly using the 
proposed method. The results of experiment 1 are 
shown in Figure 3. 
4.2 Experiment 2 
The second experiment had the Japanese to En- 
glish machine translation system ALT-J/E translate 
Japanese sentences to test various English adverb 
functions. The goal was to confirm that this adverb 
ordering method could handle various types of En- 
glish adverbs. 
The experiment considered 200 arbitrary sen- 
tences which ALT-J/E was known to analyze cor- 
rectly. This method was compared to a previous ver- 
sion of ALT-J/E which did not use adverbs' gram- 
matical functions and meanings but only this pre- 
ferred adverb positions. The result is as follows. 
Table 1: Results of Experiment 2 
Method Accuracy rate 
This Method 98% 
Previous Method 86% 
COS --- Correctly ordered sentences 
Improved Sentences: 27 (13.5%) 
Sentences changed for the worse: 3 (1.5%) 
COS 
196 
172 
5 Conclusion 
A new adverb classification based on adverb gram- 
matical functions, meanings and adverb preferred 
positions for English adverb generation in machine 
translation was proposed. The effectiveness of the 
English adverb ordering method in Japanese to En- 
glish machine translation based on the adverb clas- 
sification and the priority of the same adverb pre- 
ferred positions is shown. The priority was decided 
by examining sentences with adverbs to generate En- 
glish adverbs in Japanese to English machine trans- 
lation. If correct English adverbs are selected after 
Japanese analysis and Japanese to English transfer, 
about 97% of adverbs can be put correct positions 
in sentences by this adverb ordering method. Com- 
pared with the previous adverb ordering method, the 
accuracy rate of the proposed method is improved 
12%. The proposed method can also be used for 
adverbial prepositional phrases. 
Examined Objects 
Japanese adverb entries: 362 words 
sentences: 1,906 sentences 
English adverbs translated from 
Japanese adverbs: 1,053 
Accuracy rate 97.3% 
Adverbs generated in incorrect positions 28(2.7%) 
absolutely incorrect position: 12 (1.1%) 
strange position: 16 (1.5%) 
Figure 3: Results of Experiment 1 
This experiment confirmed that the proposed 
word ordering method can handle large amount of 
adverbs correctly. 
191 

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