SPEECH ACTS OF ASSERTION 
IN COOPERATIVE INYORMATIONAL DIALOGUE 
I.S. Kononenko 
AI Laboratory, Computer Center 
Siberian Division of the USSR Ac. Sci. 
Novoslblrsk 630090,USSR 
ABSTRACT 
Dialogue systems should provide a cooperative 
informational dialogue aimed at knowledge sharing . 
In the paper speech acts of assertion (SAA) are 
assumed to be the means of achieving this goal. A 
typology of SAAs is proposed which reflects certain 
cognitive aspects of communicative situation at 
different stages of mutual informing process. Infor- 
mation constituents of the type assertions are for- 
mally described to represent a current cognitive 
state of the speaker's knowledge base, each proposi- 
tion in it being characterized by a subjective veri-- 
similitude evaluation. The general scheme of infor- 
mation flow in the cooperative dialogue is consi- 
dered. With regard to this scheme the dialogue func- 
tions of SAAs are discussed. 
I.INTRODUCTION 
We must strive to provide dialogue systems 
with ability to interact with tile user in the kind 
of cooperative human-like dialogues of informa- 
tional type. By this type of a dialogue we mean a 
mutual informing activity of interaction partici- 
pants -- similar to Car\]son's (1984) dialogue game of 
information sharing - aimed at enriching the stock g 
of shared (mutually coordinated) knowledge. Our 
tenet in this study is that SAAs are performed in 
dialogues to approach the general goal of shared 
knowledge. The proposed typology of SAAs reflects 
their dialogue functions and contribution into the 
information flow process. 
Performing an SAA the speaker X conveys to the 
addressee Z the information about some actual situa- 
tion S, i.e. about some part of the 'world' which a 
topic of the dialogue refers to. It is assumed here 
that appropriateness of the SAA is determined by 
conditions formulated in terms of contextual proper- 
ties of the current communicative situation inclu- 
ding knowledge, beliefs, evaluations and goals of 
interaction participants (van Dijk, 1984). Certain 
cognitive aspects of eommunicatlve situation are 
considered to be a necessary precondition for SAA 
performance and simultaneously a part of SAA integ- 
ral content. 
To simulate the cognitive situation and repre- 
sent information constituents of SAA content in a 
participant's (for example, X's) knowledge base two 
cognitive components are defined. Let X be a set of 
utterances {P} whleh represents a current cognitive 
state of X (denoted as X:P). A cognitive component 
X:Z is distinguished in X which is a reflection of 
in X (X's beliefs about Z's knowledge including Z's 
beliefs about his partner X's state of knowledge), 
i.e. a set of utterances of the form P=Z:P'. Then 
tile rest of X is X's own knowledge about the world. 
Now M may be defined as a set of utterances simul- 
taneously contained in X, Z, X:Z and Z:X ( a weak 
definition of M). 
2. COGNITIVE ASPECTS OF COMMUNICATIVE SITUATION 
Tile nucleous of integral content of tile SAA 
is a propositional structure, in the simplest case, 
a proposition P which represents S in a generalized 
and semantically structured form. Besides P, the SAA 
content reflects the following aspects of communica- 
tive situation which make up a cognitive background 
for SAA generation: 
I) the speaker's state of knowledge about S, i.e. 
tile state of X, which includes X's evaluation of his 
own knowledge; 
2) the speaker's beliefs about the addressee's 
knowledge, i.e. the state of X:Z. 
2.1.Participant's knowledge. To reflect tile 
subjective nature of a participant's knowledge each 
proposition P in his individual knowledge base is 
provided with a verisimilitude evaluation (v- 
evaluation} which indicates a degree of bis certain- 
ty of whether or not P is an adequate description of 
S. It is convenient to interpret the v evaluation on 
the numerical scale (04v~l) rather than in terms of 
the traditional truth values (Truth, Falsity, Inde- 
finiteness). This allows representation of various 
degrees of belief and comparison of the partici- 
pants' knowledge: X's certainty is more, much more, 
less or equal to that of Z. The contlnuality of v- 
evaluation does not exclude selection of v-intervals 
embracing pragmatically and psychologically non-- 
distinguished scale values, each interval 
corresponding to a type of cognitive state of the 
participant. 
Different cognitive states of X are intercon- 
nected by relations regarding information flow bet- 
ween the cognitive components of X. These relations 
are expressed in terms of the following set of 
rulesl: 
(I) X:P-->X:(P,vx) 
(2) X:Z:P--~>X:P 
(3) X:Z:P--->X:Z:(P,vz'), in special case vz'=? 
(4) X:Z:(P,vz'}-->X:(P,vx), in general case Vz'~Vx 
(5) x:(P,vx)-->x:x:(P,vx) 
Note that (4) is an amplification of (2), (5) repre- 
sents the reflexivity of X. For an explanation of 
the meta-value '?' in (3) see section 2.2. To each 
rule {1}-(5) corresponds its counterpart for Z: 
(I)'-(5)' It should be born in mind tlmt X:P does 
not imply X:Z:P. 
and Z are related to M by rules (6) and (7), 
the latter corresponding to a stronger definition of 
M. These statements are valid if their premises are 
explicated in the dialogue (see section 4). 
(6} X:P&Z:P&X:Z:P&Z:X:P-->M:P 
(7) X:(P,vx)&Z:(P,vz)&X:Z:(P,Vz')&Z:X:(P,vx')& 
Vx=Vz::Vz'=Vx'=V-.->M:(P,v} 
1.The utterances of the form X:(P,vx} in the 
cognitive state representations are not provided 
with v-values which in this case are taken for 1. 
515 
The cognitive states of the X:(P,vx) type dif- 
fer In vx-values2: 
vx=l * - X is quite certain that P Is true of S; 
vx=O * - X is certain that P is false of S; 
Vx>0.5* or vx<0.5* - X is inclined P to be eva- 
luated positively (P is rather true 
than false) or negatively; 
Vx=0.5 * - both (positive and negative) evalua- 
tions are equally possible; this inter- 
val is a domain of full uncertainty, 
resulting either from the absence of any 
information in support of or against P 
or from there being much evidence both in 
favour of and against P. 
The cognitive state X:(P,vx) is a precondition 
for the performance of an SAA by X (SAA.X). Another 
necessary precondition is X's belief that Z does not 
dispose of the information about S to be conveyed by 
the SAA.X. The well-known formulation "it is not ob- 
vious to X that Z knows that P" (Searle,1969) needs 
specification since it permits several interpreta- 
tions. 
2.2.1gnorance types. We distinguish four 
ignorance situations defined by comparing the 
current state of X to that of X:Z. 
A-ignorance. X:(P,vx); X:Z+P. Considering P, X 
believes that P is not considered (or simply not 
activated) in Z. 
B-ignorance. X:(P,vx); X:Z:(P,vz'); X:Z:X:(P,vx'), 
Vx'#Vx or vx'=? P is considered by both X and Z. 
g believes that v-value of P in Z is Vz' (which 
is, possibly, not equal to Vx, by rule (4)). X 
believes also that the correct Vx-value is unknown 
to Z, i.e. Vx'6Vx/Vx'=? ('?' has been introduced 
into knowledge representation apparatus as a meta- 
value of v-evaluatlon to account for just this 
very case of ignorance). 
C-ignorance. X:(Pi,vix),vkx>0.5*; X:Z:(Pi,viz), 
viz~0.S*; X:Z:X:(Pi,vix'),vix'+vix/vix'=? X believes 
that the state of Z corresponds to disjunctive un- 
certainty: there is a set {Pi} of alternative pro- 
positional descriptions of S in Z3, none of them 
evaluated as considerably more verisimilar than the 
rest. In X v-values of the alternatives are distri- 
buted in such a way that one of them (vkx) is posi- 
tlve. In X's opinion, Z is ignorant of this 
distribution. 
D-ignorance. x:(q,vlx), vlx>0.5*; X:(P,v2x), V2x= 
l*-vlx; X:Z+Q; X:Z:(P,Vz'),Vz'>0.5*; X:Z:X:(P,Vx'), 
Vx'~V2x/Vx'=? The propositions contained in X and 
(in X's opinion) present alternative descriptions 
of S. 
The type of ignorance determines a communica- 
tive goal of the SAA, this goal subordinated to the 
general goal of the cooperative dialogue. By SAA 
performance, X intends to change Z so as to bring 
about Z's beliefs of S into line with his own 
knowledge, i.e. to approximate Z to X (or, at least, 
Z:X to X, if S has to do with the 'mental world' of 
X, i.e. X). This intention, in its turn, determines 
2.n* denotes n and the scale values close to n. 
3.The v-values of the alternative propositions are 
bound by correlation ~vi~l* ( < is the case when 
not all the alternatives are known). 
516 
a type of operational change of Z: a) to include 
information about S in Z (an inclusion operation); 
b) to exclude wrong information about S from Z (an 
exclusion operation); c) to select one of the alter- 
native descriptions of S contained in Z (a non- 
elementary selectlon operation carried out by means 
of several exclusions); d) to correct wrong informa- 
tion about S contained in Z (a non-elementary 
correction operation carried out by means of exclu- 
sion and inclusion ). 
3. SAA TYPES 
The information about the cognitive situation 
is incorporated in the integral information (infor- 
mation package - IP) to be conveyed from g to Z by 
the performance of an SAA. The information consti- 
tuents of the SAA IP are distributed between the 
three sections representing the states of M, X:Z and 
X. Their content is formed in accordance with the 
ignorance situation as X sees it by the moment of 
SAA generation. It is the content of M, X:Z and 
that determines a type of the given SAA. 
3.1.Basic SAA types. In the A-ignorance situa- 
tion a proposition P and corresponding evaluative 
information Vx is put by X under Z's 
consideration. In the B-ignorance situation it is 
evaluative information only that is introduced to Z. 
An opposition by the type of information introduced 
by an SAA (propositional + evaluative vs. evalua- 
tive) allows two basic SAA types, namely, Statements 
(S-SAA) and Evaluations (E-SAA), to be distin- 
guished. 
Statements. S-SAA is based on the assumption that 
P is not considered in Z. BV S-SAA performance, P is 
put under Z's consideration and Vx-value of P is 
communicated to Z. In general case, M is empty 
(with respect to S): the topic P hasn't been yet 
initiated in the dialogue. 
S-SAA IP: (a) M:O 
(b) X:Z+P 
(c) x:(P,vx) 
Different Vx-values determine the S-SAA sub- 
types: Indefinite Statements (vx=0.S*), Uncertain 
Statements (0*<vx<0.5* and 0.5*<vx<l*) and Certain 
Statements (vx=0 * and vx=l*). 
Examples: 
(1) It seems that John is going to leave for Paris 
to-morrow. 
(2) I am certain that Jack has passed his exam. 
(3) I don't know whether it will rain, < but I'II 
take my umbrella.> 
(4) I don't think she is married, < so it is not 
foolish for him to try to meet her again.> 
Evaluations. E-SAA is performed in the communi- 
cative situation when P has been already activated 
in M, i.e. the topic P is under consideration in the 
dialogue. No new propositional information is intro- 
duced by E-SAA. The goal of X is to introduce Vx- 
value which is not contained in Z:X, in X's opinion. 
E-SAA IP: (a) M:P 
(b) X:Z:(P,Vz') 
(c) x:(P,vx) 
(d) X:Z:X:(P,vx'), Vx'~Vx/Vx'=? 
There are Positive Evaluations (Vx>0.5*), Nega- 
tive Evaluatlons (vx<0.5*) and Indefinite Evalua- 
tions (Vx=0,5*). The consideration of possible oor- 
relations of vx and vz' allows distinguishing a 
number of E-SAA subtypes that are shown In flg.1. Of 
special interest here are Acceptance and Approval 
corresponding to Vx=Vz '. The distinctions between 
these two subtypes as well as their dialogue 
functions will be discussed in section 4. 
Examples: 
(5) Z: I am leaving for Paris. 
X: a. I see!/Are you? I didn't know that. 
(Acceptance) 
b. I know that already. 
(6) Z: It looks like John has got married. 
X: a. Really he has! <I've got to know his 
wife.> 
(Strong Confirmation) 
b. I don't think so, <he used to be a 
staunch bachelor.> 
(Weak Denial - Doubt) 
c. I wonder!/Has he? I didn't think so. 
(Doubt, vx=0.5 *) 
3.2.Non-elementary SAA types. In certain commu- 
nicative situations X performs speech acts which may 
be called non-elementary: their informational con- 
tent may be divided into several components (sets of 
information constituents) each representing the 
content of some elementary (basic) speech act. In 
the situations of C- and D-ignorance the non-elemen- 
tary SAAs (Correction and Selection) are performed, 
their information packages being the combination of 
IPs of the basic SAAs described above. 
Selection (pick). P-SAA is a means of selec- 
tion in the C-ignorance situation . In the simplest 
case M contains a set of two propositions (P,Q) and 
knowledge that only one of them is adequate to S, 
i.e. M:(P/Q,I*). By P-SAA X positively evaluates Q. 
It means a negative evaluation of P, in accordance 
with the implication ((Q,vl) --> (P,v2), vl=l*-v2). 
so, the P.-SAA IP is a combination of two E-SAA IPs, 
one of them introducing the positive evaluation of Q 
and the other negatively evaluating P; a constituent 
(b) is added to the P-SAA IP and w-values are 
specified. 
P-SAA IP: (a) M:(P,Q) 
(b) M:(P/Q,I*) 
(e) X:Z:(P,o.5*) 
(d) X:z:(q,o.5*) 
(e) X:(Q,vlx), vlx>0.5* 
(f) X:(P,v2x), V2x=l*-vlx 
(g) X:Z:X:(Q,VIx'), vlx'4vlx/vlx'=? 
(h) X:Z:X:(P,v2x'), V2x'=l*-vlx'/V2x'=? 
For example: 
(7) Z: Has Smith gone away on business or stayed 
in London? 
X: I{e has stayed, < I saw him yesterday.> 
Correction. C-SAA is performed to correct Z in 
the situation of D-ignorance. M contains P which is 
characterized by a positive v-evaluatlon in Z. 
Assuming that P is inadequate to S, X evaluates P 
negatively and introduces Q, P and Q being alterna- 
tive, in X's oplnion, i.e. X:(P/Q,I*). X believes 
that this presupposition will be accepted or ap- 
proved of by Z (included in Z) and thus become an 
element of M. The C-SAA IP combines the E-SAA IP 
(Negative Evaluation in the Denial mode) and the S- 
SAA IP (with positive evaluation of Q being intro- 
duced); a constituent (d) is added to the C-SAA IP 
and v-values are specified. 
C-SAA IP: (a) M:P 
(b) X:Z:(P,Vz'), Vz'>0.5* 
(c) X:Z+Q 
(d) X:(P/Q,I*) 
(e) x:(q,vlx), vlx>0.5* 
(f) X:(P,v2x), v2x=l*-vlx 
(g) X@:X:(P,vx'), vx'~v2x/vx'=? 
For example: 
(8) Z: You stayed at: home yesterday, I believe? 
The nomenclature of non-elementary SAAs may be 
expanded bF inclusion of alternative statements 
(combination of S-SAAs), selective statements with a 
non-siugle choice (combination of E-SAAs) etc. 
4.INFORMATION FLOW AND SAA CONTRIBUTION 
In this section we consider the process of 
information flow in the cooperative informational 
dialogue anti discuss the role of the basic SAAs in 
this process. The prohlem of information flow is 
partially analyzed by Carlson (1984) who makes suc- 
cessful use of the table and private lists metaphor. 
However, the information flow scheme proposed here 
seems to be more general as far as it takes into 
account not only the propositional but also the 
evaluative constituents of the participants' know- 
ledge. This allows distinguishing a stage of mutual 
coordination of evaluations in the scheme. Figure 2 
shows several variants of the dialogue flow of which 
certain stages are represented by Statements and 
Evaluations. 
At the beginning of the dialogue the set M is 
empty (inl). The cognitive state of X corresponds to 
A-Ignorance. This determines the appropriateness of 
S-SAA and formation of the communicative goal of 
the cooperative partner X, namely, to inform Z about 
S. X performs an S-SAA by means of which information 
about the current cognitive situation is conveyed 
from the speaker X to his addressee Z. As a result 
of S-SAA performance the cognitive situation changes 
in the following way: P is entered in g:X and, 
consequently, in Z (by rule (2)) and in X:Z; then P 
is entered in M (by (6)) and is contained there as a 
topic of tile dialogue (further the question of P 
will not be closed untill its v-evaluatlon will be 
coordinated by the participants); X:(P,vx) is en- 
tered in Z and X:Z; so, in accordance with (5) and 
(7), X's assumptions about S become mutually known 
to the partielpants, i.e. M:X:(P,Vx). 
The further course of the dialogue is deter- 
mined by the state of Z and by a type of informa- 
tional contract between X and Z (see the notion of a 
contract in Narin'yani-Simonova, 1985). This notion 
regards informational relations which hold between X 
and Z, e.g. a dominancy of X over Z, a subordinacy 
of X to Z or a neutrality between X and Z. These 
relations determine a degree of Z's confidence in X 
and a degree of Z's self-confldence. 
Let us consider several variants of the further 
progress of the dialogue. By variant 1, provided 
that an index of Z's confidence is high enough, a v- 
evaluation of P is formed in Z on the basis of Vx. 
517 
By variant 2, the formation of vz does not depend 
upon vx. In any case, the states of Z (by rule (4)') 
and of Z:X (by rule (3), In the B-ignorance mode) 
change resulting in the preconditions for E-SAA.Z. 
The E-SAA.Z is immediately aimed at the alteration 
of X:Z. By the performance of E-SAA, Z explicates 
the state of Z including Vz, after that X:Z:{P,vz), 
and the content of M changes correspondingly, i.e. 
~:z:(P,vz). 
The subtype of E-SAA.Z is determined by Vx and 
Vz correlation. In case of Vx=Vz=V the subtype is 
Acceptance (variant 1: Z accepts X's viewpoint on S) 
or Approval (variant 2: having the same assumptions 
about S, Z approves of X's viewpoint). The coinci- 
dence of X's and Z's viewpoints is now fixed in M; 
this involves the corresponding change of M (by rule 
(7}}: the topic P is closed and the constituent 
(P,v) is entered In M. So the interaction is suc- 
cessfully completed (curl} by achieving the general 
goal of the cooperative dialogue: the stock of 
shared knowledge is enriched by new mutually coordi- 
nated information about the world. 
In case of Vx+Vz the subtype of E-SAA.Z is 
Confirmation or Denial. It is obvious that Strong 
Evaluations are aimed at changing the vx-value in X. 
As for Weak Evaluations which express Z's doubts, 
their goal is determined by a degree of Z's self- 
confidence: if this index is relatively low, it is 
only X:Z that Z pretends to change; besides, he, 
probably, makes an indirect request for an additio- 
nal information which should allow him to change Vz 
for a more certain value. 
After Confirmation or Denial a stage of coordi- 
nating evaluations begins. On recieving E-SAA.Z, X 
may change Vx-value thus creating preconditions for 
the next in turn E-SAA.X. In this case ~3 
includes the E-SAA.X and the corresponding cognitive 
background. Provided that Z informationally domi- 
nates over X, a new vx-value is equal to Vz - so, 
the goal of the dialogue is accomplished (curl}. If 
nobody changes his v-value after one exchange of 
evaluative information (i.e. after the sequence of 
S-SAA.X and E-SAA.Z), ~3 is an argumentative 
interaction in the course of which one or both the 
participants try to prove their viewpoints by intro- 
ducing an additional supporting information (there 
are complex speech acts in ~3). The non-argumenta- 
tive insisting is not peculiar to the cooperative 
dialogue, it would mean going out into a kind of a 
conflict (nut 2). The above variants of the dialogue 
flow demonstrate significant distinctions between 
Statements and Evaluations as to their dialogue 
functions. The S-SAA is usually an initial dialogue 
move opening a topic of the dialogue. A secondary S- 
SAA function is to be an answer to a certain kind of 
questions ( What's happened? What's known about 
John?). Thls option is presented in the scheme by 
the dialogue beginning variant A1 which includes a 
question of Z. 
The E-SAA is a response by Its very nature. It 
reacts not only to the explicit assertive moves in 
the dialogue but also to the implicit assertions, 
e.g. to semantic presuppositions of the previous 
speech acts. In this case the E-SAA.Z follows ~2 
including some SA.X, e.g. a yes/no qnestlon of X 
which expresses just the lack of evaluative informa- 
tion (vx=0.5*). The E-SAA.Z may also be performed in 
the context of the precedlng SA.Z which has intro- 
duced P as a non-asserted propositional constituent 
518 
of an imbedding proposition {You were interested in 
John's arrival (SA.Z). John arrived (E-SAA.Z).). 
The result of SA.Z in A2 is a cognitive state 
including Z:X:(P,Vx'),Vx'=0.5* since X's viewpoint 
on S is not explicit in the dialogue (not con- 
tained in M) but is merely assumed by Z. 
The scheme of information flow discussed in 
this section accounts for functions of the basic 
SAAs in the cooperative dialogue. It appears to be 
directly extendible for the analysis of functions 
of the non-elementary SAAs. 
5.CONCLUSIONS AND FUTURE RESEARCH 
In this paper we have presented a new theore- 
tical approach to a formal description of SAA func- 
tions in the cooperative informational dialogue. It 
differs from the previous approaches in several 
ways: 
- two cognitive components in a participant's know- 
ledge base are defined to represent his own know- 
ledge as contrasted to his beliefs about his part- 
ner's state of knowledge; the rules are introduced 
describing the information flow relations 
between these components; 
- propositional and evaluative constituents are 
distinguished ill individual knowledge representa- 
tion; u notion of v-eva/nation is introduced and 
types of cognitive states described; 
- a cognitive background for SAA performance is 
represented by one of four types of ignorance; 
- a typology of SAAs is proposed which distinguishes 
between basic and non-elementary SAAs; for each SAA 
type a formal representation of its informa- 
tional content is given; 
- a scheme of information flow Js presented which 
shows different dialogue functions of SAAs; in this 
scheme a stage of introducing propositional and 
evaluative information and that of coordinating 
evaluations are considered. 
The limitations of the paper did not allow us 
to present a description of the so called particu- 
lar SAAs which are opposed to the general SAAs 
described here by the scope and character of the 
propositional information under evaluation. 
The current description can be extended in a 
variety of ways: an additional research is required 
to define the non-elementary SAAs as a sub-class of 
complex speech acts; the dialogue scheme is also to 
he extended to include the non-elementary SAAs; the 
question of how to design a dialogue model allowing 
for types of informational contracts between the 
participants deserves further attention. 
/ Acceptance ) ( Approval ) 
"~ Vx=V z q // 
\[(vx<O.5, zv'<o.5) I (vz'<vx 1--~z' ! \[(vx<O.S,,z'>O.~) I 
,.~~"'>°'5\]__ ._\l--vz'<~<~\]__ \,~>o.~.v,,<o.?.~__ 
__ 
I vx<v~° ~i I ° 5<vx<1 vz'l Ivy'<:, vz'<v~ ~ 
0.5<Vz ' <Vx \]-Vz <Vx<O. ,5 VX<I-Vz ' <Vz ' 
1,':ig. \[ : E---SAA subtypes 
 I °ut2 1 
~ :P L____\] z:(p,v~) , :x:}p,vx) I I z:x:z:(p,vz ), 
' \] Vz ' ~Vz/Vz -9 I 
Fig.2: The scheme of information flow in the cooperative ~nformational 
dialogue. 
cognitive states; 
SAAs; 
/ki gaps in the scheme; 
combination relation. 
519 

REFERENCES 
Carlson L.~ Focus and Dialogue Games, in: 
Cognitive Constraints on Communication, Vaina L. and 
Hintlkka J. (eds.). Dordrecht:Reldel,1984,p.295-333. 

~A. van (1984) . Dialogue and Cognition, in: 
Cognitive Constraints on Communication, Valna L. and 
Hintikka J. (eds.). Dordrecht: geidel,1984, p.1-17. 
Narin'yani A.S., Slmonova O~ The Structure 
of Communicative Context of Dialogue Interaction, 
Proc. ACL Europe-85,Geneva,1985. 

SearleJ. R. (1969). Speech Acts. An Essay in the 
Philoshy of Language. L. etc., 1969, - 171p. 
