DEGREES OF UNDERSTANDING 
Eva Haji~ov~ and Petr Sgall 
Faculty of Mathematics and Physics 
Charles University 
Malostransk@ n° 25 
Prague l, Czechoslovakia 
i. IntroductiOno 
Along with "static" or "declarative" 
descriptions of language system, models of 
language use (the regularities of communica- 
tive competence) are constructed. One of the 
outstanding aspects of this transfer of at- 
tention consists in the efforts devoted to 
automatic comprehension of natural language 
which, since Winograd's SHRDLU, are presented 
in many different contexts. One speaks about 
understanding, or comprehension, although it 
may be noticed that the term is used in dif- 
ferent, and often rather unclear, meanings. 
In machine translation systems, as the late 
B.Vauquois pointed out (see now Vauquois and 
Boitet, 1985), a flexible system combining 
different levels of automatic analysis is nec- 
essary (i.e.the transfer component should be 
able to operate at different levels). The hu- 
man factor cannot be completely dispensed of; 
it seems inevitable to include post-edition, 
or such a division of labour as that known 
from the system METEO. Not only the semantico- 
pragmatic items present in the source language 
structure should be reflected, but also cer- 
tain aspects of factual knowledge (see Slocum, 
1985, p.16). It was pointed out by Kirschner 
(1982, p.18) that, to a certain degree, this 
requirement can be met by means of a system 
of semantic features. For NL comprehension 
systems the automatic formulation of a partial 
image of the world often belongs to the cere 
of the system; such a task certainly goes far 
beyond pure linguistic analysis and descrip- 
tion. 
Winograd (1976) claims that a linguistic 
description should handle "the entire complex 
of the goals of the speaker" (p.269,275). It 
is then possible to ask what are the main 
184 
features relevant for the patterning of this 
complex and what are the relationships between 
understanding all the goals of the speaker 
and having internalized the system of a natu- 
ral language. It seems to be worth while to 
reexamine the different kinds and degrees of 
understanding. 
2. Understanding the sentence. 
Segmentation r disambiguation and identi- 
fication of units of the individual levels 
are the main tasks of the elementary steps of 
understanding an utterance. 
(i) The lowest step consists in the seg_i I 
mentation of the continuous flow of sound in- 
to individual phones; their sequence can be 
understood as consisting in subsequent points 
of a feature space, the individual feature 
values of the space corresponding to the dis- 
tinctive features, which have to be identi- 
fied. Disturbances oi\] this level may be due 
to noise or to physiological irregularities. 
On the phone, in a crowded room, the utterance 
I don~t understand you may mean that the 
hearer is unable to identify the uttered 
phones. 
(ii) - (iii) A phoneme may consist of sev- 
eral phonic variants, and a string of phonemes 
can be decomposed into morphs, each of which 
corresponds to a morpheme; the latter is a 
feature space again, the values of the fea- 
tures here being the semes (preterite, geni- 
hive, plural .... ). Thus, if F (a sequence of 
phones) is (the phonetic shape of) an utter- 
ance, Phone, Phoneme, Morph and Morpheme be- 
ing the sets of all phones, phonemes, morphs 
and morphemes, respectively, of the language 
1 described, we can write: 
F ~ _ _ (f\] ~.°.,fn \] , where 1 ~ n, 
P is a l\[lapping of Phone onto Phoneme 
Morph C Phoneme ~ (i.e.Morph is a proper 
subset of the set of all strings 
of phonemes\] 
M C Morph x Morpheme 
Phoneme °'= {x ~ Phoneme@; 
A,gm~ ...... ~ s ~orph(x = ~l ..... mp); 
thus Phoneme ° is the set of strings of phone- 
mes that constitute strings of morphs. The 
disambiguation identifying the string of mor- 
phemes conveyed by x can only be made, in the 
genera\] case, after the syntactic patterning 
of the sentence, its meaning and its fitting 
into the co-text and situation has been 
grasped. The steps of understanding thus can- 
not be performed in a uniform order; they are 
2 checked by means of trial and error. 
(iv) If one is reading without paying 
much attention, one "wakes up" when one's 
more or less subconscious interpretation en- 
counters an obstacle (e.g.with a garden-path 
sentence); one realizes that it is necessary 
to go back .i.n the text to where one's atten- 
tion was derailed, and read again, paying due 
respect not only to (surface) syntax, but 
also to understanding on the higher degrees. 
(v) If the hearer understands the lin- 
guistic (literal\] meaning (or, reaches a dis- 
ambiguation of the utterance), s/he under- 
stands e.g. this letter as the Objective of 
(i) and as the Actor of (2\]; further detours 
(using criteria from higher degrees) decide 
on the role of planes in a token of (3). 
(1) This letter I got only today. 
(2) This letter came only today. 
(3) Flying planes can be dangerous. 
The level of linguistic meaning (tecto- 
grammatics, underlying structure) is language 
specific and comprises the theta roles (deep 
cases, valency slots\] as well as the topic/ 
focus articulation (which is semantically re- 
levant for the scopes of operators and for 
presuppositions); see Sgall et al.(in press\]. 
without knowing the situation it is im o- 
possible to tell who is referred to by I in 
(1), what is.meant by this letter, and so on. 
Thus, considering the sense of an utterance 
(i.e., of a token of sentence in a discourse\] 
to consist in a combination of the meaning of 
the sentence with the specification of the 
reference oi_-- the expressions it contains, we 
come to a further degree of understanding, 
illustrated by Are you speaking about the let- 
ter you got from my brother?. This step leads 
us beyond the system of language, which has 
no means to identify the objects referred to. 
In the protctypical situations of communica- 
tion I is understood, since who hears the ut- 
terance \]knows who utters it. You, here, now, 
we (and thus also your, up to now .... ) are 
similar, although they are not delimited as 
for the range of reference. Without knowing 
the situation, the hearer also is unable to 
specify the reference of this letter, the 
house, a friend of mine... The sense of utter- 
ances can be identified only by means of non-- 
-linguistic clues. 
3. Understandinq in communication. 
(vi\] The identification of reference is 
conditioned by non-linguistic factors, with 
all expressions not having a unique refer- 
ence. The main factor is the speaker's assump- 
tion concerning the hierarchy of salience 
(prominence) of the items in the heater's mem- 
ory. As Haji~ovl et al. (1982; 1984\] point 
out, it refers to the most salient item, the 
table to the table activated by having occur- 
red in the focus (comment) of a preceding ut- 
terance (or by situation, common interest,.°.\] 
(vii) The next degree concerns habitual 
connotations, a possibly intended inference, 
see Winograd (1976, 275\], regular cognitive 
relationships (cf. ~frames ~ and "scenarios'\], 
and issues connected with conversational max-- 
ims and stone walling, see Joshi et al. (1984) 
(viii) Non-habitual inferences are placed 
along a scale of complexity, cf. Hintikka 
(1975), so that an elementary use of intel- 
lect (proper to most human beings, though not 
qua users of a language\] may be distinguished 
3 from conscious intellectual effort. 
Another hierarchy of inferences, concern- 
ing the difference between "what I am told" 
and "why, starts with the distinction of di- 
rect and indirect speech acts, and continues 
with that between illocution and perlocution, 
including further degrees of the type "He 
185 
wants me to react in this way; but why does 
he?" - "He wants to achieve this and this by 
my reaction; but for what purpose?",... 
4. Conclusions. 
The theory of language cannot be exclusive- 
ly based on language understanding. Coming 
back to the question put in § i, we find that 
among the degrees of understanding only those 
from § 2 immediately concern the structure 
of language, and even with them factual knowl- 
edge plays a big role. The degrees (vi) to 
(viii\]i and thus also "the entire complex of 
goals" of the speaker goes far beyond the 
domain of linguistics, contrary to Winograd. 
A theoretical account of language is a neces- 
sary ingredient of a model of comprehension; 
it allows us not to use ad hoc solutions, 
which at a later stage could prevent a useful 
generalization of the comprehension system, 
its adaptation to new applications, etc. 
When evaluating a linguistic theorv one 
should ask whether it can be embedded in a 
theory of communication; an economical ac- - 
count of topic and focus makes it possible to 
describe the meaning of a sentence as a pro- 
cedure instructing the hearer how to 
change the contents of her/his memory, and 
thus to connect the handling of sentence 
structure with that of the patterning of a 
discourse. 
Notes 
1 We neglect the cases where a phone func- 
tions in different contexts as a variant of 
two different phonemes. 
2 Disambiguation was discussed in the frame 
of neural-net linguistics and cognitive 
science by Schnelle (1984, esp.12); cf. his 
ex. Per Patient hatte einen Wachtraum VS. 
Die Kaserne... 
3 Other aspects of inferencing are studied as 
based on logical entailment, leading from the 
sense of an utterance - cf. 2 Iv) - to the 
proposition (a function from possible worlds 
into truth values); the specification of re- 
ference mostly is tacitly assumed to be pre- 
sent in a proposition. For an analysis of 
belief sentences and other "propositional" 
attitudes, as well as of such paradoxes, a~ 
that of the Liar's and for contradictions 
such as those concerning round squares and 
similar expressions it is indispensable to 
work with a clear difference between (a) the 
level of linguistic meaning (disambiguated 
underlying structure\], (b\] the layer of sense 
(including the specification of reference\], 
and (c\] the psychological domain of context 
(requiring a description of the relative 
salience of the items in the speaker's and 
heater's memories\]; cf. Sgall et al. (in 
press, Ch.l\]. 

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