DISCOURSE: CODES AND CLUES IN CONTEXTS 
Jane J. Robinson 
Artificial Intelligence Center 
SRI International, Menlo Park, California 
Some of the meaning of a discourse is encoded in its 
linguistic forms. Thls is the truth-conditional meaning 
of the propositions those forms express and entail. Some 
of the meaning is suggested (or 'implicated', as Grice 
would say) by the fact that the encooer expresses just 
those propositions in just those linguistic forms in just 
the given contexts \[2\]. The first klnd of meaning is 
usually labeled 'semantics'; it is decoded. The second 
Is usually labeled 'pragmatlcs'; it is inferred from 
clues provided by code and context. Both kinds of 
meaning are related to syntax in ways that we are coming 
to understand better as work continues in analyzing 
language and constructing processing models for 
communlcatlon. We are also coming to a better 
understanding of the relationship between the perceptual 
and conceptual structures that organize human experience 
and make it encodabla in words. (Cf. \[I\], \[4\].) 
I see thls progress in understanding not as the result 
of a revolution in the paradigm of computational 
linguistics in which one approach to natural language 
processing is abandoned for another, but rather as an 
expansion of our ideas of what both language and 
computers can do. We have been able to incorporate what 
we learned earlier in the game in a broader approach to 
more significant tasks. 
Certalnly within the last twenty years, the discipline 
of computational linguistics has expanded its view of its 
object of concern. Twenty years ago, that vlew was 
focussed on a central aspect of language, language as 
code \[3\]. The paradigmatic task of our dlsclpllne then 
was to transform a message encoded in one language into 
the same message encoded In another, using dictionaries 
and syntactic rules. (Originally, the task was not to 
translate but to transform the input as an ald to human 
translators.) 
Colncldentally, those were the days of batch 
processing and the typical inputs were scientific texts 
-- written monologues that existed as completed, static 
discourses before processlnK began. Then came 
interactive processing, brlnglng with It the opportunity 
for what is now called 'dialogue' between user and 
machine. At the same time, and perhaps not wholly 
colnoldentally, another aspect of language became salient 
for computational linguistics -- the aspect of language 
as behavior, with two or more people using the code to 
engage in purposeful ~ communication. The inputs now 
include discourse in which the amount of code to be 
interpreted continues to grow as participants in dialogue 
interact, and their interactions become part of the 
contexts for on-golng, dynamic interpretation. 
The paradigmatic task now Is to simulate in non- 
trivial ways the procedures by which people reach 
conclusions about what is in each other's minds. 
Performing this task still requires processing language 
as code, but it also requires analyzing the code in a 
context, to identify clues to the pragmatic meaning of 
its use. One way of representing thls enlarged task to 
conceive of it as requiring three concentric klnds of 
knowledge: 
a intrallngulatlc knowledge, or knowledge of the 
code 
• interllngulstlc knowledge, or knowledge of 
linguistic behavior 
• extrnllngulstlc knowledge, or knowledge of the 
perceptual and conceptual structures that 
language users have, the things they attend to 
and the goals they pursue 
The papers we will hear today range over techniques 
for identifylr~, representing and applying the various 
kinds of knowledge for the processing of discourse. 
McKeown exploits intrallngulstic knowledge for 
extralingulstic purposes. When the goal of a request for 
new information is not uniquely identlfiabte, she 
proposes to use syntactic transformations of the code of 
the request to clarify its ambiguities and ensure that 
its goal is subsequently understood. Shanon is also 
concerned with appropriateness of answers, and reports an 
investigation of the extralinguistic conceptual 
structuring of space that affects the pragmatic rules 
people follow in furnishing appropriate information in 
response to questions about where things are. 
Sidner identifies various kinds of intrallnguistic 
clues a discourse provides that indicate what entities 
occupy the focus of attention of discourse paticlpants as 
discourse proceeds, and the use of focusing (an 
extrallngulstlc prc~ess) tq control the inferences made 
in identifying the referents of pronominal anaphora. 
Levin and Hutchlnson analyze the clues in reports of 
spatial reasoning that lead to identification of the 
point of vlew of the speaker towards the entities talkeO 
about. Llke Sldner, they use syntactic clues and tlke 
Shanon, they seek to identify the conceptual structures 
that underlie behavior. 
Code and behavior interact with intentions in ways 
that are still mysterious but clearly important. The 
last two papers stress the fact that using language is 
intentional behavior and that understanding the purposes 
a discourse serves is a necessary part of understanding 
the discourse itself. Mann claims that dialogues are 
comprehensible only because participants provide clues to 
each other that make available knowledge of the goals 
being pursued. Alien and Perrault note that intention 
pervades all three layers of discourse, pointing out 
that, in order to be successful, a speaker must intend 
that the hearer recognize his intentions and infer his 
goals, but that these intentions are not signaled in any 
simple way in the code. 
In all of these papers, language is viewed as 
providing both codes for and clues to meaning, so that 
when it is used in discourse, Its forms can be decoded 
and their import can be grasped. As language users, we 
know that we can know, to a surprising extent, what 
someone else means for us to know. ~e also sometimes 
know that we don't know what someone else means rot us to 
know. As computational linguists, we are ~rying to 
figure out precisely how we know such things. 
REFERENCE3 
\[I\] Chafe, W.L. 1977. Creativity in Verbalization 
and Its Implications for the Nature of Stored Knowledge. 
In: Freedle, R.O. (ed)., <<Discourse Production alld 
Comprehension>, Voi. I, pp. 41-55. Ablex: Nor,wood, New 
Je r say. 
\[2\] Grlce, P.H. 1975. Logic and Conversation. In: 
Davldson, D. and Har~n, G. (eds.), <<The Logic of 
Gr-mmAr>. Dlcker~on: Enclno, California 
\[3\] Halitday, M.A.K. 1977. Languor as Code and 
Language as Rahavlour. In: Lamb, S. and Makkai, A. 
(eds.), <¢Semlotlcs of Culture and Lan~p~age>. 
\[~\] Mlller, G.A. and Johnson-Lalrd, P.N. 1976. 
<<Lang1~e and Perception>. Harvard University Press: 
Cambridge, Massachusetts 
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