Polyphony and Argumentative Semantics 
Jean-Michel Grandchamp* 
LIMSI-CNRS 
B.P. 133 91403 ORSAY CEDEX FRANCE 
kMevala@limsi.fr 
Abstract 
We extract from sentences a superstruc- 
ture made of argumentative operators and 
connectives applying to the remaining set 
of terminal sub-sentences. We found the 
argumentative interpretation of utterances 
on a semantics defined at the linguistic le- 
vel. We describe the computation of this 
particular semantics, based on the cons- 
traints that the superstructure impels to 
the argumentative power of terminal sub- 
sentences. 
1 Introduction 
Certain utterance structures contain linguistic clues 
that constrain their interpretation on an argumen- 
tative basis. The following example illustrates these 
constraints: 
I was robbed yesterday... 
(1) ...but luckily I had little money. 
(2) ...but luckily I had a little money. (3) 
...but unfortunately I had little money. 
(4) ...but unfortunately I had a little money. 
We describe and compute the signification of such 
sentences by specifying how the key words (in italics) 
constrain the argumentative power of the terminal 
sub-sentences (TSS) "I was robbed yesterday" and 
"I had money". They may all be interpreted in a 
relevant context, but hints for recognizing the need 
of an "odd" context are given. For instance, in (1) 
and (2), the robbery is considered bad because of the 
opposition introduced by "but", to something con- 
sidered happy because of "luckily". Holding money 
is considered good in (2) and bad in (1) because of 
the general structure of the sentence and the oppo- 
sition between "little" and "a little". In (3) and (4), 
the robbery is considered good, while in (3) money 
is normally considered good too, and in (4) (the od- 
dest) it is considered bad (imagine a speaker who 
* This research is supported by SNCF, Direction de 
la Recherche, D6partement RP, 45 rue de Londres, 75379 
Paris Cedex 08 France. 
usually likes to be robbed just to see the disappoint- 
ment because he holds no money). We see on these 
examples that TSS's are argumentatively ambiguous 
and modifiers constrain them. 
In this paper we propose, for a given utterance, 
the construction of the signification of the under- 
lying sentence, which captures its polyphonic and 
argumentative aspects. The signification of a sent- 
ence is viewed as the application of an argumentative 
super-structure to the signification of TSS's, free of 
operators or connectives. The signification must fi- 
nally be interpreted in the context of the utterance. 
2 Linguistic Background 
Our model rests on a framework inspired by Ducrot 
(1980). He defines an utterance as a concrete occur- 
rence of an abstract entity called a sentence. Under- 
standing an utterance means computing its meaning, 
which may be formalized in different contexts (such 
as speech acts or beliefs). The meaning is built from 
the context and from the signification of the sent- 
ence which :lescribes all potential uses of the lin- 
guistic matter. Ducrot's integrated pragmafics also 
claims that many phenomena usually described at 
the pragmatic level, must be described in the signi- 
fication (such as argumentation). 
Within Ducrot's framework, we use his theory of 
polyphony, topoi and modifiers. Polyphony is a 
theory that models utterances with three levels of 
characters. The talking subject refers to the per- 
son who pronounced the words. The talking subject 
introduces the speaker to whom the words are at- 
tributed (different from the talking subject in some 
cases such as indirect speech). Sentences contain li- 
teral semantic contents, each one being under the 
responsibility of an utterer. The relation between 
the speaker of a sentence and the utterer of a con- 
tent defines the commitment of the speaker to such 
a semantic content. This commitment takes one of 
the following values: identification (ID), opposition 
(OPP) and partial commitment (PC) (Ducrot, 1984; 
Grandchamp, 1994). 
Sentences are chained under linguistic warrants 
305 
called topoi (plural of topos). Topoi are found in 
words. In a sentence or a combination of sentences, 
some topoi are selected, others are not relevant to 
the discourse context. In the interpretative process, 
still others will be eliminated because of irrelevance 
to the situation. A topos is selected under one of 
its topical forms, made up of a direction (positive or 
negative) and other parameters. The topical form is 
selected with a given strength. For instance, there is 
a topos T linking wealth to acquisitions. The word 
"rich" may be seen as the positive form of T that 
says "when you are rich you may buy a lot of things". 
The word "poor" contains the negative form of the 
same topos T, that is "when you are not rich you 
may not buy a lot of things". Unlike the warrants of 
Toulmin (1958), topoi are not logic warrants. They 
may give some support for inferences, but do not 
have to. 
The strength is ruled by a subclass of operators 
called modifiers, whose semantics is described pre- 
cisely as modifying the strength of a selected topos. 
Such words include "very", "little" or "a little". Mo- 
differs combine with each other and with argument 
sentences. The strength is specified by a lexical- 
based partial ordering, producing non-quantitative 
degrees similar to Klein's (1982) . 
3 Computational Framework 
3.1 Signification of sentences 
We have discarded the utterance/sentence level of 
polyphony in order to simplify the presentation. Gi- 
ven a set of topoi T, a set of strength markers F, the 
set D={positive, negative} of directions, and the set 
V={ID,PC,OPP} of polyphonic values, we define the 
set C=TxFxDxV of argumentative cells: the topos, 
its direction, the strength and the polyphonic com- 
mitment. The signification of a sentence is defined 
as a disjunction of subsets of C. 
3.2 Syntax 
Given a sentence, we identify operators, connectives 
and modifiers, and build the A-structure of the sent- 
ence linking these linguistic clues to the TSS's. A 
sample A-structure is given in Figure 1. Connecti- 
ves constrain a pair of sentences or a sentence and 
a discursive environment, operators constrain argu- 
mentative power, and modifiers constrain only ar- 
gumentative orientation and strength. In addition, 
connectives and operators also specify the commit- 
ment of the speaker to semantic contents, by means 
of the theory of polyphony. 
3.3 Lexical contributions 
A TSS has a semantics that is described in terms 
of predications, all but one being marked by pre- 
supposition. The semantics of each predication is 
described as a set of argumentative cells. Connecti- 
ves and operators contribute to the computation of 
Connective 
but I 
\[ Unfortunately \] 
\[ Terminal sentence I Terminal sentence \[I was robbed yesterday I had 
money 
Figure 1: A-structure for "I was robbed yesterday, 
but unfortunately I had a little money" 
the signification in terms of functional transforma- 
tions of the signification along the four dimensions 
of the cells. The signification of TSS is assumed to 
be computed from the lexicon by a compositional 
process. 
3.4 Argumentative structure 
The A-structure is then considered as the applica- 
tion of an argumentative structure (made of modi- 
fiers, operators and connectives) to a vector of TSS's. 
The signification of a complete sentence is computed 
as the application of what we call the &-structure. 
A &-structure is a function that takes as many argu- 
ments as there are TSS's, and is defined by using ba- 
sic functions that are also used for the description of 
operators and connectives. Examples of basic func- 
tions that operate cell by cell are the modification of 
the polyphonic value, the direction or the strength. 
Examples of basic functions that operate on a set 
ofcells are the selection of cells with a given poly- 
phonic value, topos or direction. The ~-structure 
is computed recursively on the A-structure. As the 
identification or the contribution of an operator may 
be ambiguous, the ~-structures may contain disjunc- 
tions. 
3.5 Computation 
Given a se.atence, its (ambiguous) A- and ~- 
structures are computed. In the normal bottom-up 
process, the signification of TSS's is computed, and 
the ¢-structure is applied. The result is the (ambi- 
guous) signification of the complete sentence. 
If the signification of TSS's reflects their "stan- 
dard" or "literal" potential, the normal bottom-up 
process may fail. We wish to design &-structures so 
that they may be used for two additional tasks that 
may require a top-down process: (1) accept TSS de- 
scriptions containing free variables, and produce the 
sets of constraints on them that lead to a solution; 
(2) provide the interpretation process with a way of 
generating "unusual significations" of TSS's requi- 
red by the global effect of the ~-structure. 
306 
4 Sample Lexical Descriptions 
Connective "but": the signification of "P1 but 
P2" is computed from the significations of P1 and 
P2, with the following modifications: generate al- 
ternatives according to a partition of topoi of P1 
and P2 (whose cells have free commitment varia- 
bles) with the "opposite" relation which holds in T; 
in each alternative, commit the corresponding cells 
with the value PC for P1 and ID for P2. "P1 but P2" 
will argue in the same way as P2 alone, based on a 
topos that can be opposed to one of P1. 
Modifier "a little": the signification of "a little 
P" is the one of P where the strength of all cells is 
attenuated. 
Modifier "little": the signification of "little P" 
changes the direction of the cells into the converse 
value (anti-orientation). 
TSS "John stopped smoking": its signification 
is formed of two sets of cells, the commitment value 
being fixed to Pc for the cells from the presupposed 
predication \[John smoked before\] and left free for 
the main predication \[John does not smoke now\]. 
5 Interpretation 
The signification of TSS's, connectives, and opera- 
tors may contain instructions referring to the con- 
text for the attribution of values. The interpretative 
process must fill these holes. It also further selects 
in the sets of topoi those connected to the situation. 
It drives the top-down process for generating data 
corresponding to "odd" contexts. 
We claim that the argumentative structure of 
sentences is never questioned by the interpretative 
process, that it fully captures the argumentative po- 
tential of the sentence and that it is reliable. The 
signification is then a firm base for the computation 
of the meaning. 
6 Related Work 
Most works on argumentation define links between 
propositions at a logical level, so that linguistic stu- 
dies focus on pragmatics rather than semantics (Co- 
hen, 1987). Some ideas of Ducrot were already used 
in systems: argumentative orientation (Guez, I990) 
and polyphony (Elhadad and McKeown, 1990). Be- 
sides, Itaccah (1990) develops argumentative seman- 
tics without the need of a theory of utterance. 
7 Conclusion 
We have isolated a semantic module which allows the 
interpretation process to take into account the ar- 
gumentative constraints imposed by linguistic clues. 
We designed this module so that it starts from le- 
xical descriptions which we are able to provide ma- 
nually, and produces a structure whose interpreta- 
tion can be computed. Remaining difficulties lay in 
the linguistic theories themselves (mainly combining 
modifiers and cataloguing topoi), the signification of 
TSS's (which should be compositional) and the inte- 
gration of argumentative semantics with informative 
and illocutionary elements. 

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