THE ~ OF OOM~K/NICATIVE CONYEXr OF DIALOGUE INTERACTION 
A.S. Narin'yani, O.P. Sim~nova 
AI Laboratory, Cc~ter Center, 
Siberian Division of the USSR Ac.Sci., 
Novosibirsk 630090, USSR 
ABSTRACT 
we propose a draft scheme of the model formalizing 
the structure of o~ut~tnicative context in dialogue 
interaction. The relationships between the interact- 
ing partners are considered as system of three auto- 
mata representing the partners of the dialogue and 
enviror~ent. 
The o~l,nunicative cc~tence of the partners is de- 
fined by 
- the set M of all propositions reflecting the 
possible states of the three automata within the 
model; 
- the set K of "contracts" representing all 
kinds of htm~nn-to-htm%an relationships (social, in- 
terpersonal, professional, etc.) which include 
fixation of particular roles for the partz~-rs; 
- the set T of possible topics related to 
given "contract " 
The authors believe the system of the notions pre- 
sented may be used as a basis for forming the commu- 
nicative component in the dialogue system. 
I. INTRODUCIDRY Pd~4ARKS 
The elaboration of advanced user-computer dialogue 
systems requires the cc~m%mication la~ to be inves- 
tigated and formalized. This d~n of research has 
not yet been officially acknowledged as a part of 
computational linguistics. HzDwever, developing the 
formal models of speech interaction requires to 
take into account not only linguistic but c~ca- 
tire competence also. That is necessary for creat- 
ing natural-language systems as ~ii as any cc~li- 
cated systam of "natural" dialogue, and especially 
important in view of constructing new generation 
computers intended for mass non-programming users. 
We propose here a draft scheme of the model formaliz- 
ing the structure of c~,~nicative context in dia- 
logue interaction. The relationships between the in- 
teracting partners are considered as a system of 
three automata. TWo of them represent the agents of 
the dialogue and the third one is a model of the 
world including the envirorm~_nt of interaction and 
other agents if they participate. The autcrnaton-agent 
is the central con~ponent of the communicative compe- 
tence model. We divide m~nory of each agent into 
extracommunicative and cut~t~nicative parts. The lat- 
ter directly concerns with the relationships between 
the agents in projection onto the interaction pro- 
cess. 
Two restrictions have been accepted to simplify the 
model. 
(a) C~i,u~nicative ccrmpetences of both the agents, 
i.e. their beliefs about ccr~munication laws and ac- 
tual state of their relations are identical just up 
to current communicative act (CA) because the con- 
tents of the act (including the cc~cative con- 
tents) at the moment of its producing is known to 
the speaker only. 
(b) Receiver extracts from CA just the same informa- 
tion the speaker implies. 
2. INITIAL N317/)NS 
We shall introduce necessary notions and notations. 
Let {M} be a set of all propositions reflecting 
the possible states of the three automata within 
the model, and M be a memory representing the 
agents' mutually coordinated beliefs about the 
world. State of M at moment z (i.e. M ) is a 
consistent subset of propositions from {~}, each 
of which being characterized by index of certainty. 
The machinery of interaction between the agents is 
dcatinated by a systE~a of c o n t r a c t s. Here 
contracts represent all kinds of human-to-human re- 
lationships (social, interpersonal, business, etc.) 
For example, "chief-subordinate", "official-client", 
"friends", "married couple", "patron-ward", etc. 
Contractis_represented with a tuple 
k, X, Y. Cond, Cond-Act, Cond-Des, T, 
where 
k is a name of contract; 
and Y are roles of partners X and Y in the 
contract; 
Cor~, Cond-Act and Cond-Des are consistent 
subsets of propositions from {M}, called general 
conditions, conditions of activation and conditions 
of desactivation of the contract, respectively; 
T is a set of interact/on topics related to 
given contract. 
The interaction between the agents is realized by 
means of communicative acts (CA), in particular, 
of speech acts. Every CA is characterized with roles 
(author-receiver), aim, topic and value of phase 
function indicating the relation between CA and the 
topic (CA can be initiating, continuing, closing 
and re-initiating in respect to its topic). A sub- 
sequence of coherent cL~municative acts connected 
with the sane topic is called a t-i n t e r a c t- 
i ng. Discourse is considered as a system of ~a- 
bedded t-interactings. The simplest t-interacting 
274 
may consist of a single CA which simultaD~ously 
initiates and closes its own topic (for example, 
CA requiring no reaction fran the receiver). Topic 
is represented here by the following tuple 
t, X, Y, Cond, Aim, Scr, Cnsq, 
where 
t is a name of topic; 
X, Y and Cond have the same meaning as for 
contract in the above definition; 
Scr is a set of s c r i p t s of t-inter- 
actings which realize the topic t (a script is 
either a single CA being the simplest t-interact- 
ing mentioned above or a chain of correlated ~m- 
bedded subtopics, respectively); the scripts in 
Scr may he just listed or/and specified by means 
of a formal generative procedure; 
Cnsq is a set of all possible consequences 
of closing t, i.e. a set of modifications of the 
m~nory M resulting fran t-interactings which rea- 
lize the potential scripts of Scr; 
Aim is a subset of Cnsq which conventionally 
is considered as the aim of agent initiating the 
topic t. 
Initiating some topic t the agent chooses sane 
script from Scr he plans to realize; in general 
case a script allows several possible continuations 
at every intermediate point of its realization, 
one of these continuations corresponds to the 
script the agent plans to realize at the given mo- 
ment. 
3. OCX4~%~CATIVE CONTEXT 
Thus the ccm~micative competence of the agents 
is defined by the set {M} of propositions, the 
set {K} of contracts and the set {T} of topics 
possible for X and Y. To demonstrate the func- 
tioning of our model we shall consider the compo- 
nent of M related directly to the process of ccm- 
n~/nication. This component being called Ccrnmunica- 
tive Context (CC), includes: 
- a set Tr of current topics, i.e. the topics 
initiated before a nu,ent T and not closed yet, 
to each topic t H T current script of its reali- 
zation is put in correspondence. The topics belong- 
ing to TT are hierarchically embedded so that 
the topic t is embedded into the topic t' (or t' 
is on higher level than t) if t is initiated 
according to the current script of t'; a current 
topic/script which CA,:_ 1 belongs to,will be re- 
ferred as actual topic/script; 
- a set K T of contracts being in the activated 
state for the agent at the moment r; 
- a subset +KtC K T of contracts related to 
the topics included--in TT; i.e. the contracts im- 
mediately related to the contents of the interac- 
tion. 
The transformation of K T is defined by the fol- 
lowing rules (for each k 6 K) ; 
(a) if Cond-Act (MT) and k E K r is true, then 
the contract k is included into KT+I; 
(b) if (k E KT)&(COndk(MT)=false), i.e. conditions 
of the contract k are not fulfilled, the contract 
k is excluded from KT+ 1 ; 
(c) if Cond-DeSk(Mr)~k E K T is true, the contract 
k is excluded from KT+I; it does not mean that 
Cond-Des k (M T ) - NO Cond k (M T ) takes place. 
The rules (a) and (b) require Cond-Actk(MT)- 
-Cond k (M~). 
For the contracts in K a system of relations 
can be defined, for example: contracts kl and k2 
are mutually incompatible if 
COndk1&Condk2=false; kl is ~ n c o m p a- 
t i b 1 e with k2 if (k2 6'KTVCondk2(~)) - 
(Cond-DeSkl (M~)V NO Condkl);kl implies k2 if 
(CondklV Cond-ACtkl)- Cona-ACtk2 or k16Kt~Cond- 
-ACtk2 (M T). 
The main scheme of the considered machinery of com- 
munication can be described as follows. A current 
state M~ causes agent (X) to set scme goal; X 
fonts a plan to achieve the goal and begins to rea- 
lize it. Some step of X's plan demands to involve 
the partner Y: to perform definite action or to 
accept sane proposition as valid or to provide in- 
formation needed, etc. To get this result is the 
aim of X at the given step of this plan. To gain 
the aim, X should choose an appropriate topic 
(one of the topics with this aim). In the simplest 
case it is possible to use just the next topic t 
in the script of the higher level topic with an 
aim being more general in the X's plan than the 
current one. In this situation initiating the sub- 
topic t produces minimal modification of CC 
(which is adding t to T) and does not modify the 
set K of the activated contracts and its subset 
+K. In more complex cases to initiate an appropri- 
te topic t it is necessary to include in +K one 
of contracts from K/+K or even to activate sc~e 
new contract k', i.e. to include k' in K. Clos- 
ing a current topic t may produce sane consequen- 
ces ~ C~sqt with the corresponding modifica- 
tion of M which can lead to 
- the end of c~,,~unication, 
- a new goal for X and/or Y, 
- moving to the next subgoal in the current plan. 
In the next section we shall consider the spectrum 
of possible situations related with realization of 
current CA. 
4. MODELLING THE PROCESS 
Each current act CA r may be initiating, continu- 
ing or closing with respect to embedding topic t 
belonging to T T . 
The initiation of the topic t by CA~ may corres- 
pond to three different types of situations: "nor- 
mal order", "interruption with return", and "inter- 
ruption without return". 
(a) Normal order covers the following situations: 
- the previous act CAT- 1 has closed the topic t" 
and the topic t is the next in the script the to- 
pic t' belongs to; if t' closes simultaneously 
several consecutively embedded topics, then t is 
the next topic of the script of the lowest unclosed 
topic; 
- CAT- 1 has closed one of the highest-level to- 
pics belonging to TT- I, then (i) t belongs to 
one of the contracts frcm +Kr_ I or (ii) the contr- 
act k has been activated, but not included into 
+Kr_ I (i.e. k 6 K./+K~), or (iii) t activates 
a new contract k E~ } and includes it into K T 
and +K T (that is possible if the initiation of t 
275 
nt munent z leads to fulfillment Cond-Act k (Mw) ; 
(b) Interruption with return covers the following 
situations: the topic of the act CAT- 1 b~s nob 
been closed yet, but t is another topic of the 
same or another contract; if a change of topic is 
marked by "interruption with return", then this 
"deviation" is necessary either (i) for continuing 
the interzzA0ted topic (return after some previous 
interruption), or (ii) for the realization of the 
high-priority aim related to the new topic t; 
(c) interruption without return covers the situa- 
tions described in (b) but without the "return" 
mark as well as the following situation: the topic 
of the act CA~_ 1 is not closed and t is the 
next topic of the same or higher-level script; the 
interlnlption withot~t retttr~% us1~lly means by de- 
fault that the interrupted topic is considered to 
be closed with success or failure depending on the 
interrupted and new topics). 
The act CA~ ccntinued actual tepic t may be rea- 
lized in situations related to the normal order or 
to the return after interruption. 
(a) normal order means that CA~ continues the 
topic of the previous act CA~_ 1 ; 
(b) return after interruption means that CA~ con- 
tinues the topic remained to be unclosed ur~ "the 
interruption with return". The topic t being 
closed by the act CAT, some or all modifications 
listed in Cnsqt take place in the m~r~ry M. These 
m:~ifications reflected in MT+ 1 can cause the fol- 
lowing situations: 
(a) KT+I = K T , i .e. no contracts are activated or 
desactivated, the current script of the actual to- 
pic and higher-level topics are not alternated; 
(b) KT+I = KT, but one/some of the current scripts 
are alternated; 
(c) contract k is closed (i.e. Cond-Desk(M~+l) = 
truth) ; 
(d) other contracts are cloud and/or activated. 
The work presented is the part of the integral pro- 
ject on the lanquage interaction model being elabo- 
rated in our laboratory. 
The authors believe the system of the notions pre- 
sented may be used as a basis for forming the commu- 
nicative comp3nent in the dialogue systems includ- 
ing the natural-language interfaces. 
~CES 
I. Dijk, Teun A.van. Text and Context. Explora- 
tions in the semantics and pragmatics of 
discourse. L.-N.Y., 1977; 
2. Narin'yani, A.S., Gaft, R.I., Debrenr~, M., 
Pershina, E.L. Cu,uLunicative Interaction 
and the Functions of Speech Acts. - to ap- 
pear in "Linguistics, AI and Language Un- 
derstanding". 
3. Perret, H. Context of Understanding. Pragmatic 
and beyond. 1980. VIII. 
4. Svend, Erik Olsen. Psychology interaction and 
pragmatic linguistics. - In: Pragmalingui- 
stics, The Hague, 1979. 
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