DESIGN OF A MACHINE TRANSLATION SYST~4 FOR A SUBIASK~A(~ 
Beat Bu~, Susan Warwick, Patrick Shann 
Dalle Molle Institute for Semantic and Cognitive Studies 
University of Geneva 
Switzerland 
ABSTRACT 
This paper describes the design of a prototype 
machine translation system for a sublanguage of 
job advertis~nents. The design is based on the hy- 
pothesis that specialized linguistic subsystems may 
require special crmputational treatment and that 
therefore a relatively shallow analysis of the text 
may be sufficient for automatic translation of the 
sublanguage. This hypothesis and the desire to mi- 
nimize computation in the transfer phase has led to 
the adoption of a flat tree representation of the 
linguistic data. 
1. INTRODUCTION 
The most prcraising results in computational 
linguistics and specifically in Machine Translation 
(MT) have been obtained where applications were 
limited to languages for special purposes and to 
restricted text types (Kittredge, Lehrberger, 1982). 
In light of these prospects, the prototype MT sys- 
tem described below I should be seen as an experi- 
ment in the ecnputational trea~nent of a particular 
sublanguage. The project is meant to serve both as 
a didactic tool and as a vehicle for research in 
MT. The development of a large-scale operational 
system is not envisaged at present. The following 
research objectives have been defined for this 
project: 
- to establish linguistic specifications of the 
sublanguage as a basis for automatic processing; 
- to develop translation algorithms tailored to a 
cc~putational treatment of the sublanguage. 
The emphasis of the research lies in defining 
the depth of linguistic analysis necessary to ade- 
quately treat the ccrmplexity of the text type with 
a view to acceptable machine translation. It is the 
conjecture of our research group that, within the 
particular sublanguage defined by our corpus, ac- 
ceptable translation does not necessarily depend on 
standard linguistic structural analysis but can be 
obtained with a relatively shallow analysis. Thus, 
as a working hypothesis, the principle of 'flat 
trees' has been adopted for the representation of 
the linguistic data. Flat trees, as opposed to deep 
trees, only partially reflect the dependency strucn. 
1 Project sponsored by the Swiss government. 
ture obtained by a traditional IC-analysis. The 
adoption of flat trees goes hand in hand with the 
further hypothesis that the sublanguage can be 
translated mechanically with only minimal semm~tic 
analysis similarly to the TAUM-M~'I%0 system 
(Chevalier, et al., 1978). 
2. THE SUBLAN(ETAGE 
The corpus is taken from a weekly publication 
by the Swiss goverrm~nt announcing federal job 
openings. The wordload of this publication amounts 
to ca. I0,000 words per week; however, many of the 
advertisements are carried for several weeks. All 
job adds are published in the three national lan- 
guages: German, French and Italian, with German 
usually serving as the source language (SL), 
French and Italian as the target language (TL). 
The study is hence based on a collection of texts 
already translated by human translators. The ads 
are grouped according to profession, e.g. academic, 
technical, administrative, etc. At present, the 
corpus is limited to the domain of administrative 
positions, an example of which is given in figu- 
re I. 
Verwaltungsbeamtin 
Fonctionnaire d'administration 
Funzionaria amministrativa 
FOhren des Sekretadates eines Sektionschefs. Ausfertigen yon 
Korrespondenzen und 8erichten nach Diktat und Vorlage in 
deutscher, franz6sischer und englischer Sprache, Abgeschlos- 
sene kaufm~nnische Lehre oder Handelsschulbildung, Berufs- 
erfahrung erwOnscht, Sprachen: Deutsch, Franz6sisch. Eng- 
Iisch in Wort und Schrift. Italienisch und/oder Spanisch er- 
w0nscht. 
Diriger le secr(~tariat d'un chef de section. Dactylographier de 
la correspondance allemande, franqaise et anglaise et des rap- 
ports sous dictee ou d'apr@s manuscrits. Certificat d'ernployee 
de commerce ou dipl6me d'une ecole de commerce, Exp@- 
rience professionnelle d@sirbe. Langues: le fran~:ais, I'altemand 
et I'anglais parles et ~crits. Connaissances de I'italien ou de 
I'espagnol, voire des deux souhaitees. 
Dirigere il segretariato di un capo sezione. Stesura di corri- 
spondenza e rapporti secondo dettato o manoscritto. Tirocinio 
commerciale o formazione commerciale. Pratica pluriennale. 
Lingue: tedesco, francese, inglese (orale e seritto). Buone no- 
zioni deil'itahano e/o dello spagnolo auspicate. 
Figure i. Advertisement for an administrative 
position ("Die Stelle", 1981). 
334 
The corpus exhibits many of the textual fea- 
tures generally used to characterize a sublanguage, 
i.e. (i) limited subject matter, (ii) lexical and 
syntactic restrictions, and (iii) high frequency 
of certain constructions. AS can be seen from the 
example, the style of the sublanguage is distin- 
guished by cc~plex nominal dependencies with va- 
rious levels of coordination. In addition, most 
sentences are inoc~lete in that they consist of a 
series of nominal phrases and do not oontain a m~ 
verb; no relative phrases nor dependent clauses 
occur. The inportance of nominal constituents is 
reflected in the statistics of the German texts: 
over 55% of the words in the corpus are nouns, 
11% adjectives, 11% prepositions, 17% conjunctions ; 
verbs only make up 1% of the corpus. A ccr~parison 
with the statistics of the French and Italian 
translations reveal approximately the sane distri- 
bution except for infinitival venbs. The higher 
frequency of verbs in French and Italian is due to 
a preference for infinitival phrases in place of 
deverbal nominal constructions. Apart from this 
difference, the major textual characteristics 
carry over from source to target sublanguage there- 
by facilitating mechanical translation. 
3. BRIEF DESCRIPTION OF THE SYb-i~4 
Modem transfer-based MT systems are based on 
the following design principles : (i) modularity, 
e.g. separation of linguistic data and algorithms, 
(ii) multilinguality i.e. independent analysis, 
transfer, and generation phases, (iii) formalized 
specification of the linguistic model (Hutchins, 
1982). Although only a prototype, the system was 
• designed in accordance with these considerations. 
As to modularity, the software used is a gene- 
ral purpose rule-based transducer especially deve- 
loped for MT (Shann, Cod%ard, 1984). This software 
tool not only allows for the separation of data 
and algorithms but also provides great flexibility 
in the organization of grammars and subgrammars, 
and in the control of the cc~putational processes 
applied to them. 
As a multilingual system it is not directly 
oriented towards any specific language pair; the 
s~ne Gem1~n analysis module serves as input for 
the German-French as well as the German-Italian 
transfer module. Separate French and Italian gene- 
ration modules use only language specific knowledge 
to produce the final translation. However, the Ger- 
man analysis is indirectly influenced by target 
language considerations: the interface structure 
between analysis and transfer was defined to take 
advantage of the similarities between the three 
languages and to accommodate the differences. 
4. L~ISTIC APPBDACH: MINIMAL BUT SUFFICIENT 
DEPTH 
With the sublanguage investigated displaying 
restricted syntactic structures within a limited 
semantic dcmain, a grammar specifically tailored to 
these job advertisements can be defined. Moreover, 
the linear series of nominal phrases as well as 
the almost one-to-one lexical equivalences found 
in the SL and TL texts suggest that a shallow ana- 
lysis without a semantic component is sufficient 
for adequate translation. The flat tree represen- 
tation resulting from such a minimal depth ~;Tp~oach 
does not make any claim to linguistic generaliza- 
bility for purposes other than the translation of 
this particular sublanguage. 
4.1 Ccmputational considerations 
In a transfer-based MT system, actual trans- 
lation takes place in transfer and can be descri- 
bed as the ocr~putaticnal manipulation of tree 
structures. In the absenoe of any formal theory of 
translation for MT, and given the relatively well- 
developed analysis techniques currently available, 
a major concern in Mr research is to minimize the 
o~n~station neoessazy in the transfer phase. A 
flat tree representation provides one way of sim- 
plifying the structures to be processed; an inter- 
faoe representation defined to acocmmodate both 
SL and TL structures in the same manner, thus 
avoiding tree structure manipulation, is yet ano- 
ther means. The representation of the linguistic 
data in this system is a direct result of these 
two considerations. 
4.2 Flat trees 
The fact that the linearity of the surface 
structure constituents carries o~r from SL to the 
TLs justifies the adoption of a minimal depth ana- 
lysis. The analysis is restricted to the identifi- 
cation of the phrasal constituents and their inter- 
nal structure; dependencies holding between consti- 
tuents are only partially ccr~puted. Thus, the 
interface structure resulting from analysis and 
serving as input to transfer does not reflect a 
linguistically correct dependency structure. 
Instead, the IS respects the linear surface order 
of the constituents (with the exception of predi- 
cate groups, see below) in a flat tree represen- 
tation. 
In a flat tree, the major phrasal consti- 
tuents, in particular the prepositional phrases, 
are not attached at the node from which they de- 
pend linguistically but at specified nodes higher 
up in the tree. Schematically, the differences 
can be illustrated as follows: 
NP NP 
N PP NP pp pp \ t 
i~ N 
Fig. 2. Standard IC-tree vs. Flat tree 
The flat tree representation applies to all three 
mjor phrasal constituents defined for this cor- 
pus: (i) nominal phrases proper, (ii) deverbal 
335 
ncminal phrases, and (iii) verbal phrases. Samples 
taken from the oorpus are given below to illustrate 
each of the three constituent structures. 
(i) Ncminal phrases proper b~ve a standard noun 
phrase as their head, possibly followed by a linear 
sequence of prepositional phrases. (G~ stands for 
both standard NPs and PPs. ) 
GN ~ 
Kauf~naennische mit in der 
Ausbildung Erfahrung Verwaltung 
(ii) Deverbal nominal phrases have a deverbal noun 
as their head, followed by a linear sequence of GNs. 
GDEV 
GN (deverbal) GN GN 
Schreiben yon nach 
Texten Manuskrlpt 
(iii) Verbal phrases have a predicate as their head, 
followed by a linear sequence of GNs. (F~ enccrn- 
passes predicative participles, predicative adjec- 
tives, and infinitival predicates; the few finite 
verbs in the corpus (0.4%) are not treated.) 
GR~D 
PRED GN G~ 
erwuenscht Erfahr%ulg in der 
Datenverarbeitung 
("Erfahrung in der Datenverarbeitung erwuenscht") 
4.3 Normalized tree structures 
In order to further minimize manipulation of 
structure in transfer, the interface representation 
is also normalized for two impo~t categories in 
the sublanguage, narely deverbal ncminal phrases 
(GDEV) and noun and prepositional phrases (~N). The 
structures are defined such that they remain valid 
for both the source and target language. 
4.3.1 Devenbal nominal phrases 
A marked stylistic difference between the SL 
and the TLs occurring with high frequency in the 
corpus is the translation of a German deverbal noun 
into an infinitive in French and Italian. With the 
deverbal noun in Gennan usually serving as the head 
of a ccmplex D~minal structure with several ccsple- 
ments, the translation of the noun into an infini- 
tive in the target language changes the type of 
cc~plement structure accordingly. The complete 
linearization of the deverbal crmplements provides 
a format for acccmrcdating the target language 
infinitival construction aimed at in translation. 
Structural transfer is thus reduced to renaming 
the nodes; the normalized tree structure remains 
the same, as can be seen in the SL and TL repre- 
sentations shown below. 
GDEV 
GN ~ GN 
Ueberwachen der hinsichtlich 
Bestellungen Materiallieferungen 
Fig. 3. SL (German) deverbal ncminal phrase 
analysis. 
GPRED 
PRED GN G~ 
Surveiller les quant a la 
oc~mandes livraison du materiel 
Fig. 4. Equivalent TL (French) verbal phrase 
analysis. 
4.3.2 Noun ~hrases and prepositional phrases 
Certain noun phrases in German (e.g. genetive 
attributes) are translated into prepositional 
phrases in French and Italian. In order to avoid 
structural transfer of noun phrases into preposi- 
tional phrases and vice-versa, a normalized form 
for noun phrases has been defined which reserves 
a position in the tree for prepositions. For stan- 
dard noun phrases a special value (NIL) has been 
defined to fill the empty preposition slot. There- 
fore, in the transfer phase, a translation from a 
noun Dhrase to a prepositional phrase or vice- 
versa is merely a change in the value of the pre- 
positional slot without any change in the tree 
structure. 
PREP N ART GN ... 
Fig. 5. Example of the normalized form for 
NPs and PPs. 
4.4 CONSIDERATIONS FOR TRANSLATION 
The goal of the system, and perhaps of MT in 
general, has to be to carry over the information 
content from SL to TL, to produce output acceptable 
336 
in terms of TL conventions, and to respect the 
style of the text type. It seems that treating a 
well-defined sublanguage enhances the possibili- 
ties for an Mr system to answer these requirements. 
In fact, the sublanguage itself suggests possible 
strategies for dealing with some of the classical 
translation problems in Mr such as (i) lexical 
anbiguity, (2) translation of prepositions, and 
(3) treatment of coordination. 
4.4.1 Lexi~ip~lems 
Two well-known lexical problems in computatio- 
nal linguistics are homograph resolution and poly- 
semy disambiguaticn. Given the small number of 
possible syntactic structures in the sublanguage, 
the few homographs found in the corpus do not pre- 
sent any problems for analysis. In turn, the limi- 
ted s~mantic danain of the sublanguage cc~pletely 
eliminates multiple word senses so that the trans- 
fer of lexical meanings is basically a one-to-one 
mapping. Therefore, with the nouns serving as the 
major carriers of the textual meaning, lexical 
transfer ensures that the information content of 
the text is carried over. 
4.4.2 Translation of prepositions 
The fact that the types of nouns occurring in 
the sublanguage are restricted and repetitive and 
that the possible prepositions commanded by any 
given noun is small in nt~nber (max. 3 in the cor- 
pus) allows the adoption of a limited noun-focused 
approach for the translation of prepositions. In 
such an approach, it is the particular noun or 
noun class rather than general s~mantic features 
that determine the translation of prepositions. 
At present, the info~nation relevant to correct 
translation of prepositions is attached to indi- 
vidual noun entries in the transfer dictionary; 
semantic noun subclassification similar to other 
sublanguage research (Sager, 1982) is being 
investigated. 
4.4.3 Coordination 
With SL and TLs exhibiting parallel surface 
syntactic structure, and with inherent ambiguities 
of scope therefore carrying over, analysis of co- 
ordination remains shallow. Conjunctions and in- 
trasentential punctuation are defined functionally 
as coordinators to yield, in keeping with the flat 
tree representation, a structure such as the one 
shown below. 
PH 
O00RD G~ O00RD GN 
Sprachen : Deutsch und Englisch in Wort 
und Schri ft 
Fig. 6. Coordinated structure at sentence level. 
5. CONCLUSION 
The evidence available to-date seem~ to show 
that, for the particular sublanguage dealt with, 
correct translation is feasible under the hypo- 
theses described in this paper. The non-generali- 
zability of such an approach is quite evident; 
however, the fact that such a 'minimal depth' ap- 
proach semns to work for this particular sublan- 
guage gives substance to the impression that spe- 
cialized linguistic subsystems differ quite 
sharply, both in complexity and linguistic fea- 
tures, frc~ the standard language and may there- 
fore require special computational treatment. 
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Chevalier et al. T/K94-~'I'bO, Description du sys- 
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EidgenSssisches Personalamt (ed.). Die Stelle. 
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Grist, R., Hirsdnman, L. and Frieclman, C. 
"Natural Language Interfaces Using Limited 
Semantic Information." Proc. 9th International 
Conference on Computational Linguistics, 1982. 
Hutchins, W.J. "Tne Evolution of Madline Transla- 
tion Systems." In: Lawson, V. (ed.), Practical 
Experience of Madnine Translation, Amsterdam, 
N.Y., Oxford, 1982. 
Kittredge, R., Lehrberger, J. (eds.). Sublangua- 
@es, Studies of Lanuuage in Restricted Do- 
mai'ns, Berlin, N.Y., 1982. 
Sager, N. "Syntactic Formatting of Science Infor- 
mation." In: Kittredge, Lehrburger, 1982. 
Shann, P., Cochard, J.L. "GIT : A General Trans- 
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337 
