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A SYSTEM FOR TRANSLATING LOCATIVE PREPOSITIONS
FROM ENGLISH INTO FRENCH*
Nathalie Japkowicz Janyce M. Wiebe
Department of Computer Science Department of Computer Science
Rutgers University University of Toronto
New Brunswick, NJ 08903 Toronto, Canada M5S 1A4
nat~yoko.rutgers.edu wiebe~cs.toronto.edu
Abstract on Lakoff's ICM's. We call these entities cor.-
Machine translation of locative prepositions is ceptual representations of objects. The main
not straightforward, even between closely re- thesis of this paper is that, even though the
lated languages. This paper discusses a sys- ideal meanings of the locative prepositions we
tem of translation of locative prepositions be- studied are the same in English and in French,
tween English and French. The system is these two languages do not always conceptual-
based on the premises that English and French ize the objects involved in s scene in the same
do not always conceptualize objects in the way and that this leads to differences in the
same way, and that this accounts for the major translation of locative prepositions. This the-
differences in the ways that locative preposi- ory seems suitable to pairs of languages other
tions are used in these languages. This paper than English and French, as well.
introduces knowledge representations of con- In addition, we will also desccibe how the
ceptualizations of objects, and a method for system detects abnormalities and ambiguities
translating prepositions based on these con- using knowledge required for the translation
ceptual representations. task.
This paper is organized as follows: section
2 presents an analysis of and a solution to the
1 Introduction problem of translating locative prepositions
from English into French, section 3 presents
This paper presents an analysis of the differ- the conceptual representations of objects, sec-
ences in the uses of locative prepositions in tion 4 presents the algorithm we designed and
two languages, and then describes an auto- implemented for translating locative preposi-
matic system of translation that is based on tions, section 5 discusses the detection of ab-
this analysis. normalities and ambiguities, and section 6 is
Our research originated from the observa- the conclusion.
tion that even between two closely related lan-
guages such as English and French, locative 2 Translating Locative
prepositions of even simple sentences do not
seem to be translated from one language to Prepositions
the other in a clearly systematic and coherent
way. However, the translation becomes more We now describe the differences between En-
coherent if we introduce Herskovits' idea of glish and French locative expressions and give
the ideal meaning of a preposition (Herskovits a possible analysis of the problem. Specifi-
1986) and Lakoff's idea of Idealized Cognitive cally, we concentrate on the translation of the
Models (ICM's) (Lakoff 1987). A central part three locative prepositions 'in', 'on', and 'at',
of our research was to design entities based into the French prepositions 'dana', 'surf, and
*The research described in this paper was con- '&', in the context of simple sentences or ex-
ducted at the Uxfivez~ity of Toronto. pressions of the form:
153
(located object)(be)(locative preposition) of objects is viewed as organized around pro-
(reference object) totypes (best instances of the category) and
(located object)(locative preposition) distances from these prototypes (the shorter
(reference object) the distance of an object away from a proto-
type, the more representative of the category
the object is). In the case of prepositions, ?ro-
2.1 Examples of the problem to~ypical or ideal meanings are geometrical re-
While in the most representative uses of loca- lations between the located object, the object
tive prepositions, there is a direct correspon- whose location is being specified in the sen-
dence between English and French ('in' corre- tence, and the reference object, the object in-
sponding to 'dans', 'on' to 'sur', and 'at' to dicating the location of the located object.
'tL'), in many cases, this correspondence does A second contribution of Herskovits is her
not hold. case study of the three locative prepositions
The following pairs of sentences illustrate 'in', 'on', and 'at'. Our own study of 35 dif-
cases in which the correspondences hold: ferent cases is heavily based on this part of
Herskovits' work.
(1) The boy is in his room.
Le garcon est dazes sa chambre. 2.2.2 Grimaud's contribution
(2) The glass is on the table. Grimaud (1988) presents a linguistic analy-
Le verre est sur la table. sis of locative prepositions in English versus
(3) The secretary is at her desk. French. His theory is based on Lakoff & John-
La secr~taire est d son bureau. son (1980) and Lakoff (1987) and uses the no-
tion of com:eptua//zatioas of objects. A con-
Senten (4), (5), and (6), in contrast, ceptualization is a mental representation of an
trate cases in which the correspondences do object or an idea which takes into considera-
not hold: tion not only the =objective truth ~ about that
object or idea, but also human biological per-
(4) My friend is in the picture. ception and experience.
Mon and(e) est sur la photo. In his theory, Grimaud suggests that the
(5) The lounge chair is in the shade. cases in which the correspondences described
La chaise longue est d l'ombre. in section 2.1 do not hold are not simply ex-
ceptional but rather are due to differences
(6) Our professor is on the bus. in the ways that English and French concep-
Notre professeur est dan le bus. tualize the objects involved in the relation.
The reason why the same object can be con-
At first sight, the correspondence between En- ceptualized as different geometrical objects in
glish and French locative prepositions may different languages, given a particular situa-
seem arbitrary. Our analysis, however, reveals tion, is that objects have several properties
that coherence might be found. (or aspects) and different languages might not
choose to highlight and hide the same proper-
2.2 Analysis of the problem ties (or aspects) of a given object in a given
situation. This happens in (6), for example
Our analysis takes its principal sources in (under the interpretation in which the profes-
the works of Herskovits (1986) and Grimaud sor is riding the bus rather than being located
(1988). on the roof of the bus)-- English conceptu-
alizes the bus as a surface that can support
2.2.1 Herskovits' contribution entities, by highlighting only its bottom plat-
form, while French conceptualizes the bus as a
Herskovits (1986) contributed to the solution volume that can contain entities, by highlight-
to our problem by introducing the concept of ing its bottom surface, its sides, and its roof
the ideal meaning of a locative preposition. altogether. This leads to a difference in the
This concept is inspired by Rosch's (1977) pro- way that English and French express the spa-
totype theory, in which human categorization tial relation: English uses 'on', the preposition
154
appropriate for expressing a relation between Our final task was to design a system of
a point and a surface, and French uses 'dans' translation. Our system works as follows:
(the French equivalent of 'in'), the preposition given the source-language sentence, its objec-
appropriate for expressing a relation between tive meaning (i.e., its language-independent
a point and a volume. The appropriateness of meaning) is derived. This is done by first us-
a preposition for expressing a certain relation ing the ideal meanings of the source-language
is determined by its ideal meanings. preposition to find the conceptualization that
applies to the reference object, and then de-
2.2.3 Our synthesis riving the objective meaning of the sentence
Our task consisted of synthesizing Herskovits' from this conceptualization. (Because each
and Grimand's contributions and making this conceptualization of an object used as a ref-
synthesis suitable for a computational system, erence object corresponds to some objective
since both Herskovits and Grimaud's analyses meaning, this last step is easily performed.)
are mainly linguistic and not directly geared Given the objective meaning of the sentence,
towards computation. the conceptualization of the reference object
Our first task was to define the ideal mean- that should be used in the target language
ings of each preposition: is then found. Finally, using the list of ideal
meanings of the target.language prepositions
AT/k: together with the target-language conceptual-
ization, the system derives the preposition to
• relation between two points. be used in the target-language sentence.
ON/SUIt: 2.2.4 Other work
• relation between a point and a Independently, Zelinsky-Wibbelt (1990) took
surface whose boundaries are ir- an. approach sin~lar to ours to the problem of
relevant. translating locative prepositions. She worked
• relation between a point and a on translation between English and German
line. rather than English~and French. This sup-
IN/DANS: ports our hypothesis that the theory we use
can be extended to pairs of languages other
• relation between a point and a than English and French.
bounded surface. In addition to the types of expressions our
• relation between a point and an system translates, her system translates sen-
empty volume. tences with verbs other than 'to be'. The
reason why we chose not to process sen-
• relation between a point and a full fences using verbs other than 'to be' was to
volume. ~ study the prepositions themselves in detail,
Our next task was to develop a knowledge before addressing the more complicated prob-
representation of a conceptualization of an ob- lem of their interactions with verbs. Zelinsky-
ject, that is, a representation of the way an Wibbelt does not refer to any preliminary de-
object can be conceptualized, given a particu- tailed study of the prepositions themselves.
lar language, a particular situation, etc. Typ- We carried on a detailed bilingual study of
ically, in our application, these conceptualiza- locative prepositions by adapting and expand-
tions are geometrical objects, such as points, ing the case studies of Herskovits (1986).
lines, surfaces, and volumes.
1 Note that Herskovlts' notion of ideal meaning in- 3 The Conceptual Repre-
volves more information than ours: rather than the sentation of Objects
vague term 'relation', Herskovits identifies the specific
sort of relation that holds between the two objects,
such as coincidence, support, and containment. For The central entity in our research is the
the specific problem in translation that we address, conceptual representation of objects (or con-
such specifications axe unnecessary. They would be ceptual representation), which represents a
necessary, however, in a system designed for a deeper
understanding than ours is designed to achieve. conceptualization together with information
155
about the conditions necessary for the con- language independent). This part of the con-
ceptualization to hold. ceptual representation specifies the objective
A conceptual representation of an object is situation in which the object being conceptu-
composed of a conditional part and a descrip- alized is involved. It is central to the system
tive part. The conditional part is a list of because it is common to English and French
properties of the object and of its situation (since it describes an objective situation) and
in the sentence. The former kind of prop- is the part of the conceptual representation
erty is objective information about the ob- that allows a matching between English and
ject, such as its shape, the parts it is made French. For example, consider (4). The prop-
of, and its function. The latter properties erties of a picture that are relevant given the
are whether the object is a located or refer- objective meaning of the sentence are the fact
ence object, and whether the sentence is in that it is the re-creator of an environment,
English or French. The descriptive part is a with entities included in that environment,
description of a conceptualization of that ob- and that it is an object with a very small,
ject. This part is conceptual, rather than ob- almost non-existent, width. These properties
jective. Here follows a detailed description of are common to English and French. What dif-
conceptual representations. 2 fers are the conceptualizations: English high-
lights the first property, conceptualizing the
3.1 The conditional part picture as a volume, while French highlights
the second, considering the width to be non-
The conditional part is made up of the follow- existent and conceptualizing the picture as a
ing types of properties: surface.
* The ro/e in the sentence of the object being * World-lmowledge conditions involving the
considered (located or reference object). 3 located object of the sentence (for ~mple,
whether the located object can be supported
* The/gnguage in which the sentence is ut- by the reference object). These conditions are
tered (English or French). This condition is used to check the plausibility of a sentence
crucial to the system because not all conceptu- with respect to the located object. For ~Y,~rn.
aiizations are possible in both languages, and pie, the sentences in (6) are plausible, while
these differences account for differences in use the sentence
of the prepositions. This point is important, (7) The elephant is on the bus
for example, for pairs of sentences (4), where
a picture is conceptualized as a volume in En- is not, since an elephant is too heavy to be
glish and as a surface in French; for pairs of supported by a bus. In general, this condi-
sentences (5), where the shade is conceptual- tion is used to check for abnormalities within
ized as a Volume in English and as a point in one language rather than to account for dif-
French; and for pairs of sentences (6), where ferences between English and French. Section
a bus is conceptualized as a surface in English 5 describes how the system detects such ab-
and as a volume in French. normalities.
* The properties of the reference object that * Ez4ra-sentential constraints. Extra-
are relevant to the objective spatial relation sentential constraints are pragmatic con-
expressed in the sentence (these properties are straints, derived from the context in which
~Certain e~pects of the conceptual representations the sentence is uttered, that can influence the
were implemented for extensihillty or for the purposes choice of preposition. For example:
Of'LmhlgUlty and error detection. For the sake of com-
pletez~ss, we describe all aspects in this section, even (8) The gas station is at the freeway. [Her-
those not directly related to tr~nA|~tion (see Japkowlcz
1990 for furthe¢ explanation of these aspects). skovits 1986, p. 138]
aNote that a located object is cdways conceptual-
ized as a point. This is so because the conceptualiza- This sentence is valid only when the speaker
tion of the located object has no impact on the use pictures himself or herself as being on a tra-
of the prepositions. It is the conceptualization of the jectory intersecting the reference object at the
reference object that is relevant.
156
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