SOLVING THEMATIC DIVERGENCES IN MACHINE 
TRANSLATION 
Bonnie Doff* 
M.I.T. Artificial Intelligence Laboratory 
545 Technology Square, Room 810 
Cambridge, MA 02139, USA 
internet: bonnie@reagan.ai.mit.edu 
ABSTRACT 
Though most translation systems have some mechanism 
for translating certain types of divergent predicate-argument 
structures, they do not provide a genera\] procedure that takes 
advantage of the relationship between lexical-semantic struc- 
ture and syntactic structure. A divergent predicate-argument 
structure is one in which the predicate (e.g., the main verb) 
or its arguments (e.g., the subject and object) do not have 
the same syntactic ordering properties for both the source 
and target language. To account for such ordering differ- 
ences, a machine translator must consider language-specific 
syntactic idiosyncrasies that distinguish a target language 
¢rom a source language, while making use of lexical-semantic 
uniformities that tie the two languages together. This pa- 
per describes the mechanisms used by the UNITRAN ma- 
chine translation system for mapping an underlying lexical- 
conceptual structure to a syntactic structure (and vice ¢erea), 
and it shows how these mechanisms coupled with a set of gen- 
eral linking routines solve the problem of thematic divergence 
in machine translation. 
1 INTRODUCTION 
There are a number of different divergence types that 
arise during the translation of a source language to a tar- 
get language. Figure 1 shows some of these divergences 
with respect to Spanish, English, and German. 1 
We will look at each of these traditionally diflicnlt di- 
vergence types in turn. The first divergence type is a 
structural divergence in that the verbal object is real- 
ized as a noun phrase (John) in English and as a prepo- 
sitional phrase (a Juan) in Spanish. The second diver, 
*This paper describes research done at the Artificial In- 
telligence Laboratory of the Massachusetts Institute of Tech- 
nology. Support for this research has been provided by NSF 
Grant DCR-85552543 under a Presidential Young Investiga- 
tor's Award to Professor Robert C. Berwick. Useful guidance 
and commentary during this research were provided by Bob 
Berwick, Noam Chomsky, Bruce Dawson, Ken Hale, Mike 
Kashket, Jeff Siskind, and Patrick Winston. The author is 
also indebted to three anonymous reviewers for their aid in 
reshaping this paper into its current form. 
1Many sentences may fit into these divergence classes, not 
just the ones listed here. Also, a single sentence may exhibit 
any or all of these divergences. 
Divergence Translation 
Type Ezample 
Structural 
Conflational 
Lexical 
Categorial 
Thematic 
I saw John 
Via Juan 
(I saw to John) 
I like Mary 
Ich habe Marie gem 
(I have Mary likingly) 
I stabbed John 
Yo le di pufialadas a Juan 
(I gave knife-wounds to John) 
I am hungry 
Ieh habe Hunger 
(I have hunger) 
I like Mary 
Maria me gusta a mf 
(Mary pleases me) 
Figure 1: Divergence Types in Machine Translation 
gence is conttational. Conflation is the incorporation of 
necessary participants (or arguments) of a given action. 
Here, English uses the single word like for the two Ger- 
man words haben (have) and gem (likingly); this is be- 
cause the manner argument (i.e., the likingly portion of 
the lexical token) is incorporated into the main verb in 
English. The third divergence type is a lcxical diver- 
gence as illustrated in the stab example by the choice of 
a different lexical word dar (literally give) for the word 
stab. The fourth divergence type is categoria\] in that the 
predicate is adjectival (hungry) in English but nominal 
(hunger) in German. Finally, the fifth divergence type 
is a thematic divergence: the object (Mary) of the En- 
glish sentence is translated as the subject (Maria) in the 
Spanish sentence. 
The final divergence type, thematic divergence, is the 
one that will be the focus of this paper. We will look at 
127 
how the UNITRAN system \[Doff, 1987, 1990\] solves the 
thematic divergence problem by mapping an underlying 
lexical-conceptual structure to a syntactic structure (and 
vice versa) on the basis of a set of general linking routines 
and their associated mechanisms. The other divergences 
are also handled by the UNITRAN system, but these are 
discussed in \[Doff, 1990\]. 
It turns out there ate two types of thematic diver- 
gences that show up in the translation of a source lan- 
guage to a target language: the first type consists of a 
reordering of arguments for a given predicate; and the 
second type consists of a reordering of predicates with 
respect to their arguments or modifiers. We will look at 
examples of each of these types in turn. 
In the first case, an example is the reversal of the sub- 
ject with an object as in the English-Spanish example of 
gustar-like shown in figure 1. The predicate-argument 
structures axe shown here: 2 
\[,-MAx IN-MAX Maria\] 
\[V-MAX \[V-1 \[V-MIN me gusts\] \[P-MAX a rmq\]\]\] 
(1) \[I-MAX IN-MAX 1\] 
\[V-MAX \[`'I \[`" M~N me\] \[N~AX Mary\]\]\]\] 
Here the subject Marls has reversed places with the ob- 
ject mr. The result is that the object mi turns into the 
subject I, and the subject Marls turns into the object 
Mary. The reverse would be true if translation went in 
the opposite direction. 
An example of the second case of thematic divergence 
(not shown in figure 1) is the promotion of a comple- 
ment up to the main verb, and the demotion of the main 
verb into an adjunct position (or v/ce versa). By promo- 
tion, we mean placement "higher up" in the syntactic 
structure, and by demotion, we mean placement "lower 
down" in the syntactic structure. This situation arises 
in the translation of the Spanish sentence Juan suele ir a 
easa into the English sentence John usually goes home: 
(2) 
\[X-MAX \[~-MAX Juan\] 
\[`'-MAX \[V-* \[V-Mm suele\] 
\[,,-MAX ir\] b-MAX a casa\]\]\]\]\] 
\[z-MAx \[N-u.x John\] 
Iv.MAX \[V.X \[v-i USually Iv.raN goes\]\] IN.MAX home\]\]\]\] 
Here the main verb soler takes ir as a complement; but, 
in English, the ir predicate has been placed into a higher 
position as the main verb go, and soler is placed into a 
lower position as the adjunct usually associated with the 
main verb. The reverse would be true if translation went 
in the opposite direction. 
MOlten times a native speaker of Spanish will invert the 
subject to post-verbal position: 
\[I-MAX el IV-MAX \[V-1 \[V-Mm me gusta\] \[P-MAX aml\]\]\] 
IN-MAX Maria\]i\]. 
However, this does not affect the internal/external reversal 
scheme described here since inversion takes place indepen- 
dently after thematic divergences have been handled. 
Another example of the second case of thematic di- 
vergence is the demotion of the main verb into a com- 
plement position, and the promotion of an adjunct up 
to the main verb (or vice versa). This situation arises 
in the translation of the German sentence Ich esse gem 
into the English sentence I like eating: 
\[I.MAX IN-MAX Ich\] IV-MAX IV-! \[V-S \[V-MTN 
esse\] gem\]\]\]\] 
(3) \[X-M~x C~-MAx ~\[\] 
\[,'-MAX \[V.~ \[`'-~ ~e\] \[V-M~X eating\]\]\]\] 
Here the main verb essen takes gem as an adjunct; 
but, in English, gem has been placed into a higher po- 
sition as the main verb like, and the essen predicate 
has been placed into a lower position as the complement 
eating of the main verb. The reverse would be true if 
translation went in the opposite direction, a 
This paper will show how the system uses three mech- 
anisms along with a set of general linking routines (to 
be defined) to solve thematic divergences such as those 
that have been presented. The next section introduces 
the terminology and mechanisms that are used in the 
solution of these divergences, and, in so doing, it will 
provide a brief glimpse of how thematic divergences are 
tackled. Section 3 discusses other approaches (and their 
shortcomings) in light of the thematic divergence prob- 
lem. Finally, section 4 presents a general solution for the 
problem of thematic divergences, showing in more detail 
how a set of general linking routines and their associ- 
ated mechanisms provide the appropriate mapping from 
source to target language. 
2 TERMINOLOGY AND 
MECHANISMS 
Before we examine thematic divergences and how they 
are solved, we must first look at the terminology and 
mechanisms used throughout this paper: 4 
sit might be argued that a "direct" translation is possible 
for each of these three examples: 
(It) Mary pleases me 
(21) John is accustomed to going home 
(3,) I eat -~"ins\]y 
The problem with taking a direct approach is that it is not 
general enough to handle a wide range of cases. For example, 
gem can be used in conjunction with haben to mean like: 
Ich babe Marie gem ('I like Mary'). The literal translation, I 
have Mary likingly, is not only stylistically unattractive, but 
it is not a valid translation for this sentence. In addition, the 
direct-mapping approach is not bidirectional in the general 
case. Thus, even if we did take (1,), (2,), and (3,) to be 
the translations for (1), (2), and (3), we would not be able 
to apply the same direct mapping on the English sentences 
of (1), (2), and (3) (translating in the opposite direction) 
because we would still need to translate like and usually into 
Spanish and German. It is clear that we need some type of 
uniform method for translating thematic divergences. 
4The terms complement, specifier, and adjunct have not 
been defined; roughly, these correspond to syntactic object, 
128 
Definition 1: An LCS is a lexical conceptual 
structure conforming to a modified version of Jack- 
endoff's well-formedness rules \[Jackendoff, 1983\]. 
For example, I like Mary is represented as: 
\[State BEIdeat 
(\[Tsi~s REFERENT\], 
\[Place ATIdeat 
(\[~ka, m/:FERENT\], \[Th'-, PERSOI~\])\], 
\[, ..... LIKINGLY\])\] 
The mapping that solves thematic divergences is de- 
fined in terms of the RLCS, the CLCS, the syntactic 
structure, and the markers that specify internal/external 
and promotion/demotion information. These markers, 
or mechanisms, are specified as follows: 
MechAnism 1: The :INT and :EXT markers are 
override position markers that determine where 
the internal and external arguments will be po- 
sitioned for a given lexical root word. 
Definition 2: An RLCS is an uninstantiated LCS 
that is associated with a root word definition in 
the lexicon (i.e., an LCS with unfilled variable po- 
sitions). For example, an RLCS associated with 
the word like is: 
\[Sta*, BEId,~, 
(\[Thla, X\], 
\[Place ATIdoa, (\[Thing X\], \[Thing "Y\])\], 
\[M ..... LIKINGLY\])\] 
Definition 3: A CLCS is a composed (in- 
stantiated) LCS that is the result of combin- 
ing two or more RLCS's by means of unification 
(roughly). This is the interlingua or language- 
independent form that is the pivot between the 
source and target language. For example if we 
compose the RLCS for like with the RLCS's for I 
(\[~hi.s REFERENT\]) and Mary (\[Thing PERSON\]), 
we get the CLCS corresponding to 2" like Mary (as 
shown in definition 1). 
Definition 4: An Internal Argument Position is 
a syntactic complement for a lexical word of cate- 
gory V, N, A, P, I, or C. s 
Definition 5: An Ezternal Argument Position is 
a syntactic specifier of N for a lexical word of cat- 
egory N or a specifier of I for a lexical word of 
category V. 
Definition 6: An Adjunct Argument Position is 
a syntactic modifier that is neither internal nor 
external with respect to a lexieal word. 
Each word entry in the lexicon is associated with an 
RLCS, whose variable positions may have certain re- 
strictions on them such as internai/external and pro- 
motion/demotion information (to be described). The 
CLCS is the structure that results from combining the 
lexieal~ items of a source-language sentence into a single 
underlying pivot form. 
subject, and modifier, respectively. For a more detailed de- 
scription of these and some of the other definitions here, see 
\[Dorr, 1990\]. 
sv, N, A, P, I, and C stand for Verb, Noun, Adjective, 
Preposition, Inflection, and Complementiser, respectively. 
For example, the lexical entry for gustar is an 
RLCS that looks like the RLCS for like (see defini- 
tion 2) except that it includes the :INT and :EXT 
ma~kers: 
\[State BEldent 
(\[T~ims X :mT\], 
\[Place ATId.m, (\[Thi-s X\], \[TSiffig Y :EXT\])\], 
\[ma.ae, LIKINGLY\])\] 
During the mapping from the CLCS (shown in def- 
inition 1) to the syntactic structure, the RLCS 
for gustar (or like) is matched against the CLCS, 
and the arguments are positioned according to the 
specification associated with the RLCS. s Thus, 
the :INT and :EXT markers account for the syn- 
tactic distinction between Spanish and English by 
realizing the \[Thing REFERENT\] node of the CLCS 
(corresponding to X in the RLCS) as the inter- 
nal argument ml in Spanish, but as the external 
argument I in English; and also by realizing the 
\[T~i,s PERSON\] node of the CLCS (corresponding 
to Y in the RLCS) as the external argument Maria 
in Spanish, but as the internal argument Mary in 
English. Note that the :INT and :EXT mark- 
ers show up only in the ILLCS. The CLCS does 
not include any such markers as it is intended to 
be a language-independent representation for the 
source- and target-language sentence. 
Mechanism 2: The :PROMOTE marker associ- 
ated with an RLCS 7f places a restriction on the 
complement 7~1 of the head 7~t. 7 This restriction 
forces 7~1 to be promoted in the CLCS as the head 
7 ~. 7~ is then dropped into a modifier position of 
the CLCS, and the logical subject of 7 ~ is inher- 
ited from the CLCS associated with the syntactic 
subject of ?/I. s 
For example, the lexical entry for soler contains 
a :PROMOTE marker that is associated with the 
RLCS: \[~ ..... HABITUALLY :PROMOTE\] 
Thus, in the above formula 7"/! corresponds to 
soler, and 7~1 corresponds to the complement of 
soler. The :PROMOTE marker forces the syntac- 
tic complement 7~! to be promoted into head 
SThe lexlced-selection procedure that maps the CLCS to 
the appropriate RLCS (for like or gustar) is not described in 
detail here (see \[Dorr, 1990\]). Roughly, lexical selection is a 
129 unification-like process that matches the CLCS to the RLCS 
templates in the lexicon, and chooses the associated lexical 
words accordingly. 
position as 7 ) in the CLCS, and the head 7/I to be 
demoted into modifier position as 7/in the CLCS. 
So, in example (2) of the last section, the resulting 
CLCS is: 9 
\[,,°n, GOLo, 
(\[Thing PERSON\], 
\[P.,h TOLo~ 
(\[mac. ATLo. (\[Thi.g PERSON\], \[p,.¢. HOME\])\])\], 
\[M ..... HABITUALLY\])\] 
Here the RLCS for soler, \[M ..... HABITUALLY\], 
corresponds to 7"l and the RLCS for it, \[B,°~t GO ...\], 
corresponds to :P. In the translation to English, 
\[~ ..... HABITUALLY\] is not promoted, so it is re- 
alized as an adjunct usually of the main verb go. 
Mechanism 3: The :DEMOTE marker associ- 
ated with an RLCS 7 ~ places a restriction on the 
head 7~1 of the adjunct :Pt. This restriction forces 
7~ to be demoted into an argument position of the 
CLCS, and the logical subject of ~ to be inherited 
from the logical subject of 7"l. 
For example, the lexical entry for gem contains a 
:DEMOTE marker that is associated with the Y 
argument in the RLCS: 
\[stAte BEcl,c 
(\[Thi., x\], 
\[mac° ATm,~ (\[Thins X\], \[~,,=, Y :DEMOTE\])\], 
\[M ..... LIKINGLY\])\] 
Thus, in the above formula, T~t corresponds to 
gem and 7~! corresponds to the syntactic head 
that takes gem as an adjunct. The :DEMOTE 
marker forces the head 7~ I to be demoted into an 
argument position as 7~ in the CLCS, and the ad- 
junct 7~1 to be promoted into head position as 7 ~ 
in the CLCS. So in example (3) of the last section, 
the resulting CLCS is: 
\[s,*,, BEci,c 
(\[Thing REFERENT\], 
\[PIn°, ATci,° 
(\[T~i=g REFERENT\], 
\[,,°n, EAT (\[Thi~s REFERENT\], \[Thing FOOD\])\])\], 
..... LIKINGLY\])\] 10 
Here the RLCS for gem, \[s,a,oBEci~ .... \], 
corresponds to :P and the RLCS for es- 
sen, \[s,nt° EAT ...\], corresponds to 7"l. In the 
translation to English, \[st**e BEc~ .... \] is not de- 
moted, so it is realized as the main verb like that 
takes eating as its complement. 
PIn general, a syntactic argument ul is the canonical syn- 
tactic realization (CS~) of the corresponding CLCS argu- 
ment u. The CS7~ function is a modified version of a routine 
proposed in \[Chomsky, 1986\]. See \[Dorr, 1990\] for a more 
detailed discussion of this function. 
SThe logical subject is the highest/left-most argument in 
the CLCS. 130 
Now that we have looked briefly at the mechanisms 
involved in solving thematic divergences in UNITRAN, 
we will look at how other approaches have attempted to 
solve this problem. 
3 PREVIOUS APPROACHES 
In tackling the more global problem of machine transla- 
tion, many people have addressed different pieces of the 
thematic divergence problem, but no single approach has 
yet attempted to solve the entire space of thematic di- 
vergence possibilities. Furthermore, the pieces that have 
been solved are accounted for by mechanisms that are 
not general enough to carry over to other pieces of the 
problem, nor do they take advantage of cross-linguistic 
uniformities that can tie seemingly different languages 
together. 
Gretchen Brown has provided a model of German- 
English translation that uses lezical semantic structures 
\[Brown, 1974\]. The work is related to the model devel- 
oped for UNITRAN since both use a form of conceptual 
structure as the basis of translation. While this approach 
goes a long way toward solving a number of translation 
problems (especially compound noun disamhiguation), it 
falls short of providing a systematic solution to the the- 
matic divergence problem. This is largely because the 
conceptual structure does not serve as a common repre- 
sentation for the source and target languages. Instead, it 
is used as a point of transfer, and as such, it is forced to 
encode certain language-specific idiosyncrasies such as 
the syntactic positioning of conceptual arguments. In 
terms of the representations used in UNITRAN, this 
approach is analogous to using a language-to-language 
mapping from the RLCS's of the source language to the 
RLCS's of the target language without using an interme- 
diate language-independent structure as a pivot form. In 
sit should be noted that promotion and demotion struc- 
truces are inverses of each other. Thus, although this CLCS 
looks somewhat "English-like," it is possible to represent the 
CLCS as something that looks somewhat "Spanish-like:" 
\[State Beclze 
(\[Thing PERSON\], 
\[Place ATcirc 
(\[Thing PI~RSOiN\], 
\[Event GOLoc 
(\[Thing PERSON\], 
\[Path TOLo© 
(\[Place ATLoc (\[Thing PERSON\], \[Place HOME\])\])\])\])\], 
\[M ..... HABITUALLY\])\] 
In this case, we would need to use the :DEMOTE marker (see 
mechanism 3) instead of the :PROMOTE marker, but this 
marker would be used in the RLCS associated with usually 
instead of the RLCS associated with soler. The justification 
for using the "English-like" version for this example is that 
the \[Manner HABITUALLY\] constituent is generally thought of 
as an aspcctual clement associated with a predicate (e.g., in 
German, the sentence would be Ich gehe gewJhnlich nach 
Hause ('I go usually home')); this constituent cannot be 
used as a predicate in its own right. Thus, the compli- 
cated "Spanish-like" predicate-argument structure is not a 
likely conceptual representation for constructions that use 
\[Manner HABITUALLY\]. 
1°The default object being eaten is \[Thing FOOD\], although 
this is not syntactically realized in this example. 
this approach, there is no single language-independent 
mechanism that links the conceptual representation to 
the syntactic structure; thus, it is necessary to hand- 
code the rules of thematic divergence for English and 
German, and all divergence generalizations are lost. 
In 1982, Lytinen and Schank developed the MOP- 
TRANS Spanish-English system based on conceptual de- 
pendency networks \[Lytinen & Schank, 1982\]. 11 This 
approach is related to the UNITRAN model of transla- 
tion in that it uses an interlingual representation as the 
pivot from source to target language. The key distinc- 
tion is that the approach lacks a generalized linking to 
syntax. For example, there is no systematic method for 
determining which conceptual argument is the subject 
and which is the object. This means that there is no 
uniform mechanism for handling divergences such as the 
subject-object reversal of example (1). 
The LMT system is a logic-based English-German ma- 
chine translator based on a modular logical grammar 
\[McCord, 1989\]. McCord specifically addresses the prob- 
lem of thematic divergence in translating the sentence 
Mir gef~llt der Waged (I like the car). However, the so- 
lution that he offers is to provide a "transfer entry" that 
interchanges the subject and object positions. There are 
two problems with this approach. First it relies specifi- 
cally on this object-initial ordering, even though the sen- 
tence is arguably more preferable with a subject-initial 
ordering Der Wagen gef~llt mir; thus, the solution is 
dependent on syntactic ordering considerations, and will 
not work in the general case. Second the approach does 
not attempt to tie this particular type of thematic di- 
vergence to the rest of the space of thematic divergence 
possibilities; thus, it cannot uniformly translate a con- 
ceptually similar sentence Ich \]ahre das Wagen gem (I 
like to drive the car). 
4 THEMATIC DIVERGENCES 
In section 1, we introduced some examples of thematic 
divergences, and in section 2 we described some of the 
mechanisms that are used to solve these divergences. 
Now that we have looked at other machine transla- 
tion approaches with respect to the thematic divergence 
problem, we will look at the solution that is used in the 
UNITRAN system. 
Recall that there are two types of thematic diver- 
gences: 
1. Different argument positionings with respect 
to a given predicate. 
2. Different predicate positionings with respect 
to arguments or modifiers. 
The first type covers the case of argument positions that 
diverge; it is accounted for by the :INT and :EXT mark- 
ers. The second type covers the case of predicate posi- 
tions that diverge; it is accounted for by the :PROMOTE 
11Several researchers have worked within this framework 
including Goldman \[1974\], Schank & Abelson \[1977\], and 
many others. 131 
and :DEMOTE markers. Together, these two types of 
divergences account for the entire space of thematic di- 
vergences, since all participants must be one of these two 
(either an argument, or a predicate, or both). 
In both cases of thematic divergence, it is assumed 
that there is a CLCS that is derived from a source- 
language RLCS that is isomorphic to the correspond- 
ing target-language RLCS (i.e., the variables in the 2 
RLCS's map to the same positions, though they may 
be labeled differently). Furthermore, it is assumed that 
thematic divergence arises only in eases where there is a 
logical subject. 
A CLCS with logical subject w, non-subject 
arguments Zl, z2,..., z~, ..., z=, and modifiers 
nl, n2 .... , nz ..... n,~ will look like the structure shown 
in (4), where the dominating head 7 ~ is a typed primitive 
(e.g., BEcirc): 
(4) \[7~ w, zl,z2 .... , zk,...,z~,nl,n2,...,n,...,n,~\] 
In order to derive the syntactic structure from the 
CLCS, we need a mapping or linking rule between the 
CLCS positions and the appropriate syntactic positions. 
Roughly, this linking rule is stated as follows: 
General Linking Routine G: 
(a) Map the logical subject to the external argu- 
ment position. 
(b) Map the non-logical-subjects to internal ar- 
gument positions. 
(c) Map modifiers to adjunct positions. 
(d) Map the dominating head to the phrasal head 
position. 
G is used for the second half of translation (i.e., mapping 
to the target-language structure); we also need an in- 
verse routine that maps syntactic positions of the source- 
language structure to the CLCS positions: 
Inverse Linking Routine G-l: 
(a) Map the external argument to the logical sub- 
ject position. 
(b) Map the internal arguments to non-logical- 
subject positions. 
(c) Map adjuncts to modifier positions. 
(d) Map the phrasal head to the dominating head 
node. 
In terms of the representation shown in (4), the 
and ~-1 mappings would be defined as shown 
in figure 2.12,1s'14 Note that wl, zlt .... ,zM,...,znt, 
and nll,...,nlt,...,nm ! are the source-language re- 
alizations of the corresponding CLCS tokens w, 
zl, .. •, zk, .. •, zn, and nl, ..., nz, ..., n,~; similarly, wit, 
zllI, • • • , z~tll, • • •, Znll , and dill , ..., dill , ..., nmll are 
target-language realizations of the same CLCS tokens. 
This assumes that there is only one external argument 
and zero or more internal arguments. We will now look 
zc.:%...~ \] n,..=n,...%,\] \[Y-MAX~'\[\[X-M'N'p'\] ' ' ' ' ' ' 
4 s S'' ,,~'" ~,~ f~. -1 
• • % • ..,, .. -.. ~,~; 
• -,. ,.. ,... ) 
II II # II II IS \[Y-MAX ~/\] \[\[X-MIN? \]Zl...Zk...Zn\] TI, I...Y~I..OFI, m\] 
Figure 2: Mapping From Source to Target via the CLCS 
at a formal description of how each type of thematic di- 
vergence is manifested. We will then See how the general 
linking routines described here take the syntactic mech- 
anisms into account in order to derive the appropriate 
result. 
4.1 Divergent Argument Posltionings 
In order to account for the thematic revcrsa3 that shows 
up in the gustar-l~e example of (1), we must have a 
mechanism for mapping CLCS axgumcnts to different 
syntactic positions. In terms of the CLCS, we need to 
allow the syntactic realization of the logical subject w 
and the syntactic realization of a non-subject argument 
(say zk) to switch places between the source and target 
language. 
Figure 3 shows how this type of argument reversal is 
achieved. The :INT and :EXT markets axe used in the 
RLCS specifications as override markers for the G and 
G-I routines: the :INT marker is used to map the logi- 
ca3 subject of the CLCS to an internal syntactic position 
(and vice versa). Thus, steps (a) and (b) of ~ and g-z 
are activated differently if the RLCS associated with the 
phrasal head contains either of the :INT or :EXT over- 
ride mechanisms. Note that the CLCS is the same for 
12The convention adopted in this paper is to use ul for the 
source-language realization, and url for the target-language 
realization for a CLCS argument u. 
13Adjunction has been placed to the right at the maximal 
level. However, this is not the general case. A parameter 
setting determines the side and level at which a particu- 
lar adjunct will occur (as discussed in \[Doff, 1990\]). The 
configuration shown corresponds to the spec-initial/head- 
initial case. The other three possible configurations are: 
\[Y-MA~ ~' Ix-, ~' ~'...~' \[X-M~ ~"\]\] m' ..... ~,'\], 
\[Y-MAX IX-1 \[X-MIN PI\] Zl! g2f....Znl \] '~! I"~11 , .... am'\], 
and \[Y.~Ax \[x-, z,, ~, ...-.., Ix.MxN ~"\]\] ~' m', .... n,,,,\]. 
Finally, the order of the zit's and nfl's is not being addressed 
here; this is determined by independent principles also dis- 
cussed in \[Dorr, 1990~. Regardless of these syntactic vari- 
ations, the ~ and ~- routines operate uniformly because 
they are language-independent. For simplicity, the spec- 
inltlal/head-initial configuration will be used for the rest of 
this paper. 
X~In addition to realization of arguments, the dominating 
CLCS head (~P) must also be realized as a lexical word (PI 
in the SOVLrce language and ~P, in the target language). The 
syntactic category of this lexical word is X, and the maximal 
projection is Y-MAX. In general, Y = X unless X is a Verb 
(in which case, Y is the Inflection category). 132 
RLCS entry for~)l: 
\[p (w :IN~),Z,, (z k :~xz),...,z, ~,,...,~,...,~.,. \] 
RLCS entry for p#.. 
\['P w, z,,...,z,,...,~.,,~ ,,...,,~,,...,,,. \] 
I \[Y-MA~Z~\[\[X-MIN I " ' I ' , • p \]~,,,...z; \] ,~,...,~,...,~ \] 
.... }0' 
\[P ~,z,,...,zk,...,~.,~,,...,~,...,~. \] 
q ll II # "q ll II II II II \[Y-MAX ~O \[\[X-MINP \]ZI...Zk...Z\] nl...~l..."m\] 
Figure 3: Mapping From Source to Target for Divergent 
Arguments 
RLCS entry for gustar: 
\[BE \[X :IN'P\] \[AT IX\] \[Y :EXTI\] LIKINGLY\] 
RLCS entry for like: 
\[BE \[X\] \[AT \[X\] \[Y\]\] LIKINGLY\] 
\[I-MAX \[N-MAX Marlsa~ - ........ ... 
\[V-MAX \[V-1 \[V-MIN me gusta\]', 
\[P-MAX a ml~\]\]\] ', ~0" J 
\[BE \[RZFERBNT\] \[AT \[REFERENT\] \[PERSON\]\] LIKINOLY\] ' ) 
\[I-MAX \[N-MAX I\] Iv 
\[V-MAX \[Vol \[V-MIN like\] \[N-MAX Mary\]\]\]\] 
Figure 4: Translation of Mar{a me gusta a m~ 
both the source and target language; only the RLCS's in 
the lexica3 entries need to include language-specific in- 
formation in order to account for thematic divergences. 
Now using the ~ and ~-1 routines and the overriding 
:INT and :EXT mechanisms, we can show how to ac- 
count for the thematic divergence of example (1). 
Figure 4 shows the mapping from Spanish to English 
for example (1). is'Is Because the Spanish RLCS 
includes the :INT and :EXT markers, the G-z routine 
activates steps (a) and (b) differently: the external argu- 
ment Marfa is mapped to a non-logical-subject position 
\[Thins PERSON\], and the internal argument mlis mapped 
to the logical subject position \[Thi, g REFERENT\]. By 
lSBecause of space limitations, we will illustrate the three 
examples (I), (2), and (3) in one direction only. However, 
it should be clear that the thematic dlvergcnces are solved 
going in the opposite direction as well since the g and g-1 
mappings are reversible. 
18A shorthand notation is being used for the RLCS's and 
the CLCS. See section 2 for a description of the actual rep- 
resentations used by the system. 
contrast, the English RLCS does not include any spe- 
cial markers. Thus, the G routine activates steps (a) 
and (b) normally: the logical subject \[Thi.g REFERENT\] 
is mapped to the external argument I, and the non- 
logical-subject \[Thl,s PERSON\] is mapped to the internal 
position Mary. 
Now we have seen how argument positioning diver- 
gences are solved during the translation processJ ¢ In 
the next section, we will look at how we account for the 
second part of thematic divergences: different predicate 
positionings. 
4.2 Divergent Predicate Positionings 
In the last section, we concentrated primarily on the- 
matic interchange of arguments. In this section, we will 
concentrate on thematic interchange of predicates. In 
so doing, we will have accounted for the entire space of 
thematic divergences. 
There are two ways to be in a predicate-argument rela- 
tionship: the first is by complementation, and the second 
is by adjunction. That is, syntactic phrases include base- 
generated complements and base-generated adjuncts, 
both of which participate in a predicate-argument struc- 
ture (where the predicate is the head that subcategori~.es 
for the base-generated complement or adjunct), ts 
In order to show how predicate divergences are 
solved, we must enumerate all possible source- 
language/target-language predicate positionings with 
respect to arguments z~, z2,..., zk, ..., z,+ and mod- 
ifiers nt, n~,..., nz, ..., n~. In terms of the syn- 
tactic structure, we must examine all the possible 
positionings for syntactic head 7~t with respect to 
its complements zzt, z~t,...,zht,...,znt and adjuncts 
rill, n2 I, ... ,nil,... , nrnl. 
xrIt should be noted that the solution presented here (as 
well as that of the next section) does not appeal to an already- 
coded set of conceptual "frames." Rather, the syntactic 
structures are derived procedurally on the basis of two pieces 
of information: lexical entries (i.e., the RLCS's) and the re- 
sult of composing the RLCS's into a single unit (i.e., the 
CLCS). It would not be possible to map declarativelp, i.e., 
from a set of static source-language frames to a set of static 
target-language frames. This is because the ~ and ~-1 rou- 
tines are intended to operate recursively: an argument that 
occurs in a divergent phrasal construction might itself be a 
divergent phrasal construction. For example, in the sentence 
le saele gustar leer a Jnan ('John usually likes to read'), there 
is a simultaneous occurrence of two types of divergences: the 
verb soler exhibits a predicate positioning divergence with 
respect to its complement gustar leer a Juan, which itself ex- 
hibits an argument positioning divergence. The procedural 
mappings described here are crucial for handling such cases. 
iSWe have left out the possibility of a base-generated spec- 
ifier as a participant in the predicate-argument relationship. 
Of course, the specifier is an argument to the predicate, but 
it turns out that the syntactic specifier, which corresponds to 
the logical subject in the LCS, has a special status, and does 
not participate in predicate divergences in the same way as 
syntactic complements and adjuncts. This will be illustrated 
shortly. 133 
RLCS entry for~l: \[P \] 
RLCS entry for nil; 
\[n I :PROMOTE\] 
RLCS entry for ~t~ 
\['P,o,~,,...,z+,...,z,,,n~,...,n,,...,,+. \] 
(~) 
Y-MAX I I I I I I I I tO \[\[X-MIN RI\]~ ZI...Z k...Zn\] 1"1, I ...~m\] 
r w,z~,...,z+,...,z,,rt,,...,n,+,...,n,,, \] 
%~,~ %%% -.. ,. ~ 
tUII ~ ~ II II II U It" "~ I ; \[Y-MAX \[\[X-MINP \]Z,...Zk...Z \] n...~lt...t1,,,,\] 
RLCS entry forPl: (b) 
\[P 
RLCS entry for'P 
t t!~tt I I I t \[Y-MAx w \[\[X-M,N Z,...Z\] 
i S } G" 
\] 
w \[IX-Mere/" IZc..Zv..Zl "l"""t'"'%J 
Figure 5: Mapping From Source to Target for Divergent 
Predicates 
There are a large number of possible positionings that 
exhibit predicate divergences, but only two of them arise 
in natural languageJ 9 It turns out that the soler- 
usually example of (2) and the gem-like example of (3) 
are representative of the space of possibilities of predi- 
cate divergences. The source-language/target-language 
predicate positionings for these two cases are represented 
as shown in figure 5. Part (a) of this figure accounts for 
the translation of usually to soler (or vice versa), and 
part (b) accounts for the translation of like to gem (or 
vice versa). 
The ~ and ~-1 routines do not take into account the 
predicate divergences that were just presented. As in the 
case of argument divergences, predicate divergences re- 
quire override markers. The :PROMOTE marker is used 
to map a modifier of the CLCS to a syntactic head posi- 
tion (and vice versa). The :DEMOTE marker is used to 
map a non-subject argument of the CLCS to a syntac- 
tic head position (and vice versa). Thus, steps (c), and 
19 There is not enough space to elaborate on this claim here. 
See \[Doff, 1990\] for a detailed discussion of what the possible 
positionings are, and which ones make sense in the context 
of linguistic structure. 
RLCS entry for ir : 
\[GO /Xl \[To \[AT \[Xl \[Villi 
RLCS entry for go: 
log IX\] \[TO \[AT \[Xl \[YIIII 
RLCS entry for soler: 
\[HABITUALLY :PROMOTE\] 
RLCS entry for usually. 
\[HABITUALLY\] 
{I-MAX IN-MAX Juan\] 
IV-MAX \[V-MIN suele\] ....... . l 
{V-MAX \[V-MIN ir\]\[P-MAX ~,¢~a\]\]\]\]l~ "~ 
\[GO \[PERSON\] \[TO \[AT \[PERSON\] \[HOME\]\]\] HABITUALLY 
{I-MAX {N-MAX John\] ~." "'. at ,, 
{V-MAX \[v-, \[V.I usually \[V-MIN goesl\] 
\[N-~AX home\]\]\]\] 
RLCS entry for geru: 
{BID \[X\] \[AT \[X\] \[V :DEMOTE\]\] LIKINGLY\] 
RLCS entry for/{ke: 
\[BE \[X\] \[AT \[X\] \[Y\]\] LIKINGLY\] 
{I-MAX IN-MAX IC~I\] 
{V-MAX \[V-I\[V-I\[V-MIN esse\] gern\]\]\]\] "I 
\[BE {REFERENT\] 
\[AT \[REFERENT\] \[EAT \[REFERENT\] {FOOD\]\]\] 
%%LIKINGLY\]• ~, -*x ~ ~" "" 1 
{I-MAX {N-MAX I\] .... " 
Iv-MAx iv. \[V-MIN ~kel \[V-MAX~ati-gllll 
Figure 6: Translation of Juan suele ira casa 
(d) of the ~ and ~-1 routines axe activated differently 
if the RLCS associated with the phrasal head contains 
the :PROMOTE override marker, and steps (b) and (d) 
of these routines axe activated differently if a phrasal 
adjunct contains the :DEMOTE override marker. 
Now using the ~ and G-t routines and the overriding 
:PROMOTE and :DEMOTE mechanisms, we can show 
how to account for the thematic divergences of exam- 
ples (2) and (3) (see figures 6 and 7, respectively). 
In figure 6, the Spanish RLCS for soler includes the 
:PROMOTE marker. Thus, steps (c) and (d) of f -1 are 
overridden: the internal argument ira casa is promoted 
into the dominating head position \[B,o,, GOt.el; and the 
phrasal head suele is mapped into a modifier position 
\[M ..... HABITUALLY\]. By contrast, the English RLCS 
does not include any special markers. Thus, the G rou- 
tine activates steps (c) and (d) normally: the dominating 
head \[E,o., GOL.c\] is mapped into the phrasal head goes; 
and the modifier \[M ..... HABITUALLY\] is mapped into 
an adjunct position usually. 
In figure 7, the German RLCS for gem includes the 
:DEMOTE marker (associated with the variable Y). 
Thus, steps (b) and (d) of ~-1 are overridden: the 
phrasal head esse is demoted into a non-logical-subject 
position \[E,,n, EAT\]; and the adjunct gem is mapped into 
the dominating head position Is,,,, BEtide\]. By contrast, 
the English RLCS does not include any special mark- 
ers. Thus, the G routine activates steps (b) and (d) 
normally: the dominating head Is,.. BEoI,©\] is mapped 
into the phrasal head like; and the non-logical-subject 
\[E,,n, EAT\] is mapped into the internal position eating. 
5 SUMMARY 
This paper has presented a solution to the problem of 
thematic divergences in machine translation. The so- 
lution has been implemented in UNITRAN, a bidirec- 
tional system currently operating on Spanish, English, 
and German, running in Commonlisp on a Symbolics 
3600 series machine. We have seen that the procedures 
involved are general enough to operate uniformly across 
different languages and divergence types. Furthermore, 
the entire space of thematic divergence possibilities is 
134 
Figure 7: Translation of Ich habe Marie gem 
covered in this approach without recourse to language- 
specific routines or transfer rules. In addition to the- 
matic divergences, the system handles the other diver- 
gence types shown in figure 1, and it is expected that 
additional divergence types will be handled by means of 
equally principled methods. 
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