The Semantics of Motion 
Pierre Sablayrolles 
I R I T -- Universit~ Paul Sabatier 
118 route de Narbonne 
31062 Toulouse - France 
phone : +33 61 55 67 64 
fax : +33 61 55 83 25 
e-mail : sablay@irit.fr 
Abstract 
In this paper we present a semantic 
study of motion complexes (ie. of a mo- 
tion verb followed by a spatial preposi- 
tion). We focus on the spatial and the 
temporal intrinsic semantic properties of 
the motion verbs, on the one hand, and 
of the spatial prepositions, on the other 
hand. Then we address the problem of 
combining these basic semantics in or- 
der to formally and automatically de- 
rive the spatiotemporal semantics of a 
motion complex from the spatiotempo- 
ral properties of its components. 
1 Introduction 
Most of natural languages provide two types of 
lexical items to describe the motion of an entity 
with respect to some location: motion verbs (to 
run; to enter) and spatial prepositions (from; 
towards). Motion verbs can be used directly with 
a location, when they are transitive (to cross the 
town) or with a spatial preposition, when they are 
intransitive (to go through the town). The latter 
case is more interesting: most of the French mo- 
tion verbs are intransitive and the interaction be- 
tween motion verbs and spatial prepositions gives 
detailed informations about the way human bee- 
ings mentally represent spatiotemporal aspects of 
a motion. When we describe a motion, the fact 
to choose a verb instead of another, a preposition 
instead of another, a syntactic structure instead 
of another, reveals our mental cognitive represen- 
tation. We claim that natural languages can be 
considered as a trace of these representations, in 
which it is possible, with systematic and detailled 
linguistic studies, to light up the way spatiotem- 
poral properties are represented and on which ba- 
sic concepts these representations lie. We present 
such linguistic investigations on French motion 
verbs and spatial prepositions and the basic con- 
cepts we have found. We also address composi- 
tional semantics for motion complexes (ie. a mo- 
tion verb followed by a spatial preposition) and 
show that the complexity and the refinements of 
the linguistic studies presented just before are jus- 
tified and required at the compositional level in 
order to capture the different behaviours in the 
compositional processes that exist with the French 
language. We also compare with the English lan- 
guage and draw some conclusions on the benefits 
of our approach. 
2 Lexical Semantics for Motion 
Verbs 
Following Gruber (1965), Jackendoff (1976), 
Boons (1985), we approach motion verbs in terms 
of some "localist semantical" role labels. The lin- 
guistic study of French intransitive motion verbs 
(see eg. (Asher & Sablayrolles, 1994a)) we have 
realized has allowed the definition of an ontology 
for "location" in three basic concepts: 
• locations which are concrete places (a room; 
a house; a street); 
• positions which are parts of a location (the 
position where I am in this room); 
• postures which are ways to be in a position 
(to be standing, sitting, lying). 
With the help of this ontology we have realized 
a typology for intransitive motion verbs. We dis- 
tinguish 4 categories on the basis of which kind of 
"location" they intrinsically refer to. 
• Change of location (COL) verbs (entrer- 
to enter; sortir-to go out) denote a change 
of location. When we enter some place or go 
out of some place, we have different spatial 
relation with the location (ie. inside/outside) 
before and after the n~otion. 
• Change of position verbs (voyager-to 
travel; courir-to run) denote a change of po- 
sition. When we travel or run, we go from 
some part to another part of a same global 
location. Such verbs do not behave all homo- 
geneously. 
- Some denote a change of position which 
always occur (voyager-to trave D. For 
281 
example, we cannot say voyager sur 
place-to travel in place. We call these 
verbs change of position (CoPs) 
verbs. 
- Others denote only possible change of 
position (courir-to run). For example, 
we can say courir sur place-to run 
in place. We call these verbs inertial 
change of position (ICoPs) verbs. 
• Change of posture (CoPtu) verbs 
(s'asseoir-to sit down; se baisser-to 
bend down). They denote a change of the 
relations between the parts of an entity. 
For the following, we will focus on CoL verbs 
(the Change of Location verbs), mainly because 
they are rich in spatiotemporal informations, but 
also because we have at disposal exhaustive lists 
of French CoL verbs. We have realized a system- 
atic and fine linguistic study on these verbs, look- 
ing carefully at each of them, one by one (and we 
have 440 CoL verbs in French), in order to extract 
their intrinsic spatiotemporal properties. These 
semantic properties can be characterized by a re- 
structuration of the space induced by the so-called 
reference location (lref) (cf. (Talmy, 1983)). 
This lref, implicitly suggested by each CoL verb, 
can be either the initial location (as with partir- 
to leave; sortir-t0 go out), or the path (passer, 
traverser-to pass through) or the final location 
(arriver-to arrive; entrer-to enter) of the mo- 
tion. Indeed, verbs like sortir intrinsically sug- 
gest a location of which we have gone out. This 
space, induced by the lref, is characterized by most 
of the authors in the literature by a two-part spa- 
tial system consisting in the inside and the outside 
of the lref. We propose to refine this structure 
with two new concepts, required to distinguish 
minimal pairs like sortir (to go out)/partir (to 
leave), and entr r (to ent r)/atterir (to land). 
These concepts are: 
1. a limit of proximity distinguishing an outside 
of proximity from a far away outside; indeed, 
if sortir simply requires to go out of the lref, 
partir in addition forces the mobile to go 
sufficiently far away from that lref. 
2. an external zone of contact required by verbs 
like atterir for which the final location is 
neither the lref (in contrast with entrer) or 
the outside (or proximity outside) of the lref 
(in contrast with s'approcher-~o approach). 
We have so defined a structuration of the space 
based on 4 zones : 
* the inside; 
o the external zone of contact; 
o the outside of proximity; 
o the far away outside. 
This structuration is close to the way J ackendoff 
and Landau (1992) encode the space induced by 
the reference object introduced by a static spatial 
preposition. As we have come to these distinctions 
by examining different linguistic material, we con- 
clude that language structures space in the same 
way whatever sort of lexical items (motion verbs 
(dynamic)/(static) spatial prepositions) we exam- 
ine. This has allowed us to classify CoL verbs into 
10 classes on the basis of which zones the mobile 
is inside, at the beginning and at the end of its 
motion. Note that all the geometrical possibilities 
are not lexicalized in French. 
3 Lexical Semantics for Spatial 
Prepositions 
We have followed the same approach with French 
spatial prepositions, but using a structuration of 
the space induced by the location introduced in 
the PP by the preposition, and not induced by the 
lref as for verbs. Following Laur (1993), we con- 
sider simple prepositions (like in) as well as prepo- 
sitional phrases (like in front o\]). We have classi- 
fied 199 such French prepositions into 16 groups 
using in addition of our zones two other criteria: 
• prepositions can be: 
- positional (like in) 
- directional (like into) 
• directional prepositions can be: 
- Initial (like from) 
- Medial (like through) 
- Final (like to) 
depending if they focus on the initial location, 
on the path or on the final location of the 
motion. 
4 Compositional Semantics for 
Motion Complexes 
The linguistic studies, used for the typologies of 
CoL verbs and spatial prepositions, have been re- 
alized on verbs considered without any adjuncts, 
in their atemporal form and independently of any 
context, on the one hand, and on prepositions 
considered independently of any context, on the 
other. This methodology, discussed in Borillo & 
Sablayrolles (1993), has allowed us to extract the 
intrinsic semantics of these lexical items. 
Since natural languages put together verbs and 
prepositions in a sentence, we have developped 
a formal calculus (see (Asher & Sablayrolles, 
1994b)), based on these two typologies, which 
computes, in a compositional way, the spatiotem- 
poral properties of a motion complex from the se- 
mantic properties of the verb and of the prepo- 
sition. For reason of space we cannot detail our 
formalism here, but we intend to present it in the 
talk. 
282 
The semantics of a motion complex is not 
the simple addition of the semantics of its con- 
stituents. On the contrary, it is the result of a 
complex interaction between these properties. It 
is often the case that from this interaction appear 
new properties that belong neither to the verb or 
the preposition. These new properties are only 
the result of the interaction of the verb with the 
preposition. 
Let us consider for example the following VP: 
sortir dans le jardin-to go out into the gar- 
den. The verb sortir-to go out implicitly sug- 
gests an initial location; the preposition darts- 
(which means in, but which is translated here by 
into) is a positional preposition and, as so, only 
denotes the static spatial relation inside. The lo- 
cation le jardin-the garden is the final location 
of the motion. This final information was con- 
tained neither in the verb or in the preposition. 
This information is the result of the interaction 
of the verb sortir-to go out with the preposition 
dans-in/qnto. 
Note that the combination for such items does 
not behave the same in English, where the final 
information is explicitly brought by the preposi- 
tion into, which is a directional preposition, and 
where this particular combination does not create 
new information. 
This shows the neccesity to take into account 
such language specific behaviour in natural lan- 
guages understanding systems and in natural lan- 
guages machine translation. We formalize with 
11 axioms in a non-monotonic first order logic the 
behaviour of all possible kinds of verb-preposition 
association for the French language. We use non- 
monotonic logic in order to represent defensible or 
generic rules and also in order to encode defaults 
about lexical entries. 
These axioms are based on the lexieal semantics 
of CoL verbs and of spatial prepositions. They 
also take into account the syntactic structure of 
the sentence (we have supposed an X-bar syntax 
with a VP internal subject, though this is not es- 
sential) and the links which exist at the level of 
diseours between this sentence and the previous 
and following sentences of the text. These links, 
called discourse relations, are basic concepts on 
which texts are structured (cf. (Asher, 1993)). 
5 Conclusion 
The study and the first results we have here pre- 
sented cover from lexical semantics to discourse 
structures, with strong interactions between these 
two ends. Indeed, lexical informations can be used 
to disambiguate the structure of the discours, as 
well as discourse relations can be used to dis- 
ambiguate lexical entries, as shown in (Asher & 
Sablayrolles, 1994b). Our work is based on sys- 
tematic and very detailed linguistic studies which 
lead to rather complex computations for calculat- 
ing the spatiotemporal semantics of a motion com- 
plex. But we have seen that this level of detail and 
complexity is necessary if one want to understand, 
to formalize and to compute a right spatiotempo- 
ral semantics for motion complexes. We continue 
our investigations on two directions: 
1. we compare our results with similar works 
in course of realization on the Basquian lan- 
guage (by Michel Aurnague) and on the 
Japanese language (by Junichi Saito); 
2. we use the results presented here for refin- 
ing the notions of the Aktionsart, where the 
structuration of the space in 4 zones can be 
used to distinguish sub-classes inside the tra- 
ditional well known classes of aspectual stud- 
ies. 
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