DONNELLAN'S DISTINCTION 
AND A COMPUTATIONAL MODEL OF REFERENCE 
Amichai Kronfeld Artificial Intelligence Center 
SRI International and 
333 Ravenswood Avenue 
Menlo Park, CA 94025 
kronfeld~sri-warbucks 
Center for the Study of 
Language and Information 
Stanford University 
Stanford, CA 94305 
ABSTRACT 
In this paper, I describe how Donnellan's distinction between 
referential and attributive uses of definite descriptions should 
be represented in a computational model of reference. After 
briefly discussing the significance of Donnellan's distinction, I 
reinterpret it as being three-tiered, relating to object represen- 
tation, referring intentions, and choice of rehrring expression. 
I then present a cognitive model of referring, the components 
of which correspond to this analysis, and discuss the interac- 
tion that takes place among those components. Finally, the 
implementation of this model, now in progress, is described. 
INTRODUCTION 
It is widely acknowledged that Donnellan's distinction \[7\] be- 
tween referential and attributive uses of definite descriptions 
must be taken into account in any theory of reference. There 
is not yet agreement, however, as to where the distinction fits 
in a theoretical model of definite noun phrases. For Cohen 
\[4\], the intention that the hearer identify a referent consti- 
tutes a crucial difference between the referential and the at- 
tributive. Barwise and Perry \[3\], on the other hand, treat 
their value-loaded/value-free distinction as the central feature 
of the referential versus the attributive. However, as pointed 
out by Grosz et al. \[9\], this analysis ignores an essential aspect 
of Donnellan's distinction, namely, the speaker's ability, when 
using a description referentially, to refer to an object that is 
independent of the semantic denotation. 
The problem of determining the correct interpretation of 
Donnellan's distinction is of considerable importance. First, 
Donnellan's distinction seems to violate the principle that ref- 
erence to physical objects is achieved by virtue of the descrip- 
tive content of referring expressions. This principle can be 
found practically everywhere -- for example, in Frege's sense 
and reference, Rusell's theory of descriptions, and Searle's 
speech acts. In the referential use of definite descriptions, 
however, reference seems to be established independently of 
descriptive content. If I say ~The man over there with a glass 
of white wine is..., ~ I may be successful in my act of referring 
-- regardless of whether the person over there is a man or a 
woman, the glass is full of wine or grape juice, the color of 
the beverage is white or red, and so on. This, if accepted, 
has far-reaching consequences for the meaning of referring ex- 
pressions, for the logical structure of propositions, and for the 
theory of propositional attitudes. 
Second, the referential/attributive distinction forces us to 
reconsider the division between semantics and pragmatics. It 
seems that a speaker's intentions in using a referring expression 
do make a semantic difference. If I say ~Smith's murderer is 
insane," meaning that whoever murdered Smith is insane (the 
attributive case), what I say is true if and only if the one and 
only murderer is insane. If, on the other hand, my intention is 
to use the definite description referentially (referring to, say, 
Tom, who is accused of being the culprit), what I say is true 
if and only if Torn is indeed insane -- whether he is the mur- 
derer or not. Unless we understand the interaction between 
conventional meaning and a speaker's intentions in such cases, 
we cannot hope to construct an adequate model of referring 
and language use in general. 
Finally, Donnellan's distinction brings to the fore the role 
of identification in the speech act of referring. Both Strawson 
and Searle (\[17,16\]) attempted to analyze referring in terms 
of identification and identifying descriptions. But Donnellan 
has pointed to what seems to be a clear distinction between 
eases in which identification is required (referential use) and 
thor in which it is not (attributive use). This calls for a new 
analysis of the speech act of referring, one that does not rely 
on identification as a central concept, l 
In this paper, I present a general framework for treating 
Donnellan's distinction. In particular, I contend the following: 
1. The apparent simplicity of the referential/attributive dis- 
tinction masks three aspects of the problem of reference. 
In a sense, it is not one distinction but three: the first 
has to do with representations of objects, the second -- 
with referring intentions, the third -- with the choice of 
referring expressions. 
2. These three distinctions are independent of one another, 
and should be handled separately. Each is relevant to a 
different component of a plan-based model of reference: 
the data base, the planner, and the utterance generator, 
respectively. 
3. Although the three distinctions are mutually independent, 
tThese comments, naturally, only touch the surface. For an extensive 
discussion of the significance of the referential/attributive distinction see 
my thesis \[141. For a discussion of the role of identification in referring, 
see the paper coauthored by Appelt and me on this topic 12\]. 
186 
they of course interact with one another. The notion of a 
conversationally relevant description provides a basis for 
explaining how the interaction operates. 
In the following sections, the three aspects are presented, 
their interactions discussed, and an initial attempt to achieve 
an implementation that takes them into account is described. 
CRITERIA 
How is the referential to be distinguished from the attributive? 
Two criteria are usually offered: 
1. Even though, when used attributively, the description 
must denote the intended referent, in the referential use 
this is not necessary. 
2. In the referential use, the speaker has a particular object 
in mind, whereas in the attributive he does not. 
These criteria have been taken to be equivalent: any use 
of a definite description that is referential according to one 
criterion should also be classified as referential according to 
the other (and similarly for the attributive use). However, 
the equivalence of the two criteria is really an illusion: some 
uses of definite descriptions are referential according to one 
criterion, but attributive according to the other. For example, 
let us suppose that John, a police investigator, finds Smith's 
murdered body, and that there are clear fingerprints on the 
murder weapon. Now consider John's utterance: "The man 
whose fingerprints these are, whoever he is, is insane." Note 
that John intended to speak of Smith's murderer, and he may 
very well have been successful in conveying his intended ref- 
erent, whether or not the fingerprints indeed belonged to the 
murderer. Hence, according to the first criterion, the descrip- 
tion, "The man whose fingerprints these are," was used refer- 
entially. On the other hand, John did not have any particular 
person in mind. Hence, according to the second criterion, the 
description must have been used attributively. 
Many, including Donnellan, regard the second criterion as 
the more significant one. But even this criterion is given two 
conflicting interpretations. On the one hand, ~having a par- 
ticular object in mind" is taken as an epistemic concept: this 
view holds that one can have a particular object in mind while 
referring only if one knows who or what the referent is. On the 
other hand, the criterion also receives what I call the modal 
interpretation. According to this reading, the referential use of 
a definite description is simply tantamount to employing the 
description as a rigid designator. Obviously, the two interpre. 
tations are not equivalent. As Kaplan demonstrates \[lll, one 
can use a description as a rigid designator without having any 
idea who the referent is. 
Thus, there are three aspects of Dounellan's distinction that 
should be carefully separated. These aspects can be repre- 
sented in terms of three dichotomies: 
* Having knowledge of an object versus not having such 
knowledge (the epistemie distinction). 
,, Using a description as a rigid designator versus using it 
as a nonrigid one (the modal distinction). 
s Using a definite description "the ~" to refer to whoever or 
whatever the ~ may be, versus using "the ~" to refer to 
an object z, whether or not z is indeed the ~ (the speech 
act distinction). 
THREE COMPONENTS 
The epistemic, modal, and speech act distinctions correspond 
to three components that a plan-based model of reference must 
possess, z Any such model must contain the following: 
1. A database that includes representations of objects 
2. A planner that constructs strategies for carrying out re- 
ferring intentions 
3. An utterance generator that produces referring expres- 
sions 
Let us call these the database, the planner, and the utterance- 
generator, respectively. The next three sections describe a cog- 
nitive model of referring that incorporates these components. 
Object Representations 
Objects are represented to agents by terms. These terms are 
grouped into individuatin9 sets. An individuating set for an 
agent S is a maximal set of terms, all believed by S to be 
denoting the same object. For example, for John, the police 
investigator, the set {Smith'n murderer, the man who~e finger- 
prints these are} is an individuating set of Smith's murderer. 
The incredibly complex cluster of internal representations un- 
der which, for instance, John's mother would be represented 
to him is also an individuating set, although it would be im- 
practical to enumerate all the terms in this set. 
An individuating set is grounded if it contains either a per- 
ceptual term or a term that is the value of a function whose 
argument is a perceptual term. For example, a set containing 
the description "your father" is grounded, since it contains a 
terms that is the result of applying the function FATHER-OF 
to a perceptual term representing you. 
It should be emphasized that an individuating set is the 
result of the speaker's beliefs, not a mirror of what is actually 
the case. A speaker may possess two distinct individuating sets 
that, unbeknownst to him, determine the same object (e.g., 
Oedipus's representations of his mother and his wife). On 
the other hand, a speaker may possess an individuating set 
containing two or more terms that actually denote different 
objects. Moreover, the object that an agent believes to be 
denoted by the terms of some individuating set may not exist 
in the actual world. 
Whether or not an agent can have knowledge of the referent, 
or know who or what the referent is (the epistemic distinc- 
tion}, depends on the nature of the relevant individuating set. 
In a computational model, we can place a number of restric- 
tions on individuating sets to reflect various epistemological 
intuitions. For example, we may require that, for an agent to 
be able to manipulate an object, the relevant individuating set 
must contain a perceptual term, or that, for an agent to know 
eFor a plan-based model of referring, definite noun phrases, and speech 
acts in general, see articles by Appelt, Cohen, Cohen and Levesque, Cohen 
and Perrault (\[1,4,.5,6\]). 
187 
DISTINCTION INTERPRETATION 
Epistemic Type of individuating set 
Modal Type of referring intentions 
Speech act Choice of definite noun phrase 
I COMPONENT 
Database 
Planner 
Utterance generator 
Table 1: Donnellan's distinction, its interpretation\[s), and the corresponding computational components. 
who a certain person is (relative to purpose P), the relevant 
individuating set must include a privileged term determined 
by P, or that, for an agent to have knowledge o fan object, the 
relevant individuating set must be grounded, and so on. 
Since individuating sets are part of the database, this is 
where the epistemlc distinction belongs. 
Referring Intentions 
A speaker may have two distinct types of referring intentions. 
First, he may select a particular term from the relevant indi- 
viduatlng set, and intend this term to be recognized by the 
hearer. Second, the speaker may intend to refer to the ob- 
ject determined by an individuating set, without intending any 
particular term from the set to be part of the proposition he 
wants to express. Consider, for example, the following two 
statements: 
1 The author of Othello wrote the best play about jealousy. 
2 Shakespeare was born in Stratford-upon.Avon. 
In making both statements, a speaker would normally be re- 
ferring to Shakespeare. But note the difference in referring 
intentions between the two: in the first statement, the speaker 
selects a particular aspect of Shakespeare, namely, the fact 
that he is the author of Othello, and intends the hearer to 
think of Shakespeare in terms of this aspect. In the second 
statement, the speaker does not select any particular aspect 
of Shakespeare from the relevant individuating set. Indeed, 
he may not care at all how the hearer makes the connection 
between the name "Shakespeare" and the referent. 
The two types of referring intentions yield two distinct types 
of propositions. When the speaker does not intend any par. 
ticular aspect of the referent to be recognized by the hearer, 
the proposition expressed in this way is singular, that is, it 
does not contain any individual concept of the referent. Con- 
sequently, the referring expression chosen by the speaker (be 
it a proper name, a demonstrative, or even a definite descrip- 
tion) is used as a rigid designator, which means that it picks 
out the same individual in all possible worlds where the ref- 
erent exists. On the other hand, if a particular aspect of the 
referent is meant to be recognized by the hearer, then the in- 
dividual concept corresponding to that aspect is part of the 
proposition expressed and should therefore be taken into ac- 
count in evaluating the truth value of what is said. Thus, it 
is the speaker's referring intentions that determine whether or 
not he will use a definite description as a rigid designator (the 
modal distinction). Since referring intentions are represented 
in the planner, this is where the modal distinction belongs. 
Note that the two types of referring intentions can be de- 
scribed as intentions to place constraints on the way the hearer 
will be thinking of the referent. In Appelt and Kronfeld \[2\], 
this is generalized to other referring intentions -- for example, 
the intention that the hearer identify the referent. 
Referring Expressions 
Once the speaker decides what his referring intentions are, 
he must choose an appropriate referring expression. Usually, 
if a particular aspect of the referent is important, a suitable 
definite description is employed; otherwise a proper name or 
a demonstrative may be more useful. However, such a neat 
correlation between types of referring expressions and referring 
intentions may not happen in practice. In any case, as we 
shall see in the next section, the speaker's choice of a referring 
expression constitutes an implicit decision as to whether the 
denotation of the referring expression must coincide with the 
intended referent (the speech act distinction). The choice of 
referring expression is naturally made within the utterance 
generator, where the speech act distinction is represented. 
By way of summary, Table I shows how Donnellan's distinc- 
tion, in its reinterpreted form, is related to a plan-based model 
of reference. 
RELEVANT DESCRIPTIONS 
Kripke and Searle \[12,15\] explain the referential use as a case 
in which speaker's reference is distinct from semantic refer- 
ence. This leaves an important question unanswered: why 
must speaker's reference and semantic reference coincide in 
the attributive use? s 
Sometimes two definite descriptions are equally useful for 
identifying the intended referent, yet cannot be substituted 
for each other in a speech act. The description employed, be- 
sides being useful for identification, has to be relevant in some 
other respect. Consider the utterance: "New York needs more 
policemen.* Instead of "New York," one might have used "The 
largest city in the U.S2 or "The Big Apple," but "The city 
hosting the 1986 ACL conference needs more policemen" won't 
do, even though this description might be as useful in identi- 
fying New York as the others. The latter statement simply 
conveys an unwarranted implication. 
As a generalization, we may say that there are two senses 
in which a definite description might be regarded as relevant. 
First, it has to be relevant for the purpose of letting the hearer 
know what the speaker is talking about. 4 A description that 
is relevant in this sense may be called functionally relevant. 
S~eond, as the example above indicates, a description might 
exhibit a type of relevance that is not merely a referring tool. 
~As redefined by the ~pcech act distinction. 
4Whether the hearer is also expected to identify the referent is a seps- 
r~te issue. 
188 
A description that is relevant in this noninstrumental sense 
might be called conversationally relevant. 
Every use of a definite description for the purpose of refer- 
ence has to be functionally relevant. But not every such use 
has to be conversationally relevant. If indicating the referent 
is the only intended purpose, any other functionally relevant 
description will do just as well. 
In other cases, the description is supposed to do more than 
just point out the intended referent to the hearer. Consider 
the following examples: 
3 This happy man must have been drinking champagne. 
4 The man who murdered Smith so brutally has to be insane. 
B The winner of this race will get $I0,000. 
In these examples, the speaker implicates (in Grice's sense} 
something that is not part of what he says. In (3), it is impli- 
cated that the man's happiness is due to his drinking. In (4), it 
is implicated that the main motivation for believing the mur- 
derer to be insane is that he committed such a brutal homicide. 
The implicature in (5) is that the only reason for giving the 
winner $10,000 is his victory in a particular race. In all these 
cases, what is implicated is some relationship between a spe- 
cific characteristic of the referent mentioned in the description 
and whatever is said about that referent. In such cases, it does 
matter what description is chosen, since the relevance is both 
functional and conversational. No other description, even if it 
identifies equally well, can be as successful in conveying the 
intended implicature. 
The conversationally relevant description may not be men- 
tioned explicitly, but rather inferred indirectly from the con- 
text. In the fingerprint example, the speaker uses the descrip- 
tion, The man whose fingerprints these are, but the conversa- 
tionally relevant description is nevertheless Smith's murderer. 
Thus, there are three general ways in which a speaker may 
employ a referring definite description: 
1. If the discourse requires no conversationally relevant de- 
scription, any functionally relevant one will do. This cov- 
ers all standard examples of the referential use, in which 
the sole function of the definite description is to indicate 
an object to the hearer. 
2. If a conversationally relevant description is needed, the 
speaker may do either of the following: 
(a) Use the description explicitly. This is what is done 
in standard examples of the attributive use. 
(b) Use a different, functionally relevant description. 
The speaker can do so, however, only if the context 
indicates the aspect of the referent that corresponds 
to the conversationally relevant description. This ex- 
plains the ambiguity of the fingerprint example. As 
the definite description uttered is only functionally 
relevant, its use appears to be referential. Yet, un- 
like the referential case, a conversationally relevant 
description is implied. 
In sum, when the description used is conversationally rel- 
evant, the speaker intends that the specific way he chose to 
do his referring should be taken into account in interpreting 
the speech act as a whole. Consequently, if the description 
fails, so does the entire speech act. On the other hand, if the 
description is only fimctionally relevant, the context may still 
supply enough information to identify the intended referent. 
INTERACTIONS 
When a speaker plans a speech act involving reference to an 
object, he must determine whether or not a conversationally 
relevant description is needed. However, the nature of the in- 
dividuating set, on the one hand, and constraints on choices of 
referring expressions, on the other, may influence the speaker's 
planning in various ways. For example, if the individuating set 
contains only one item, say, the shortest spy, the definite de- 
scription "the shortest spy" must be conversationally relevant. 
This is true both on formal and pragmatic grounds. From 
a formal standpoint, the description is conversationally rele- 
vant by default: no other functionally relevant description can 
be substituted because no such description is available. From 
a pragmatic standpoint, the description "the shortest spy" is 
very likely to be conversationally relevant in real discourse, 
simply because all we know about the referent is that he is the 
shortest spy. Thus, whatever we may have to say about that 
person is very likely to be related to the few facts contained in 
the description. 
Even if it is clear that a conversationally relevza~t description 
is needed for the speech act to succeed, constraints on choices 
of referring expressions may prevent the speaker from using 
this description. One such constraint results from the need 
to identify the referent for the hearer. If the conversationally 
relevant description is not suited for identification, a conflict 
arises. For example, in "John believes Smith's murderer to be 
insane," the speaker may be trying simultaneously to represent 
the content of John's belief and to identify for the hearer whom 
the belief is about. Sometimes it is impossible to accomplish 
both goals with one and the same description. 
IMPLEMENTATION 
This paper is part of an extensive analysis of the referen- 
tial/attributive distinction, which I use in the construction of a 
general model of reference \[13\]. My ultimate research objective 
is to provide s computational version of the reference model, 
then to incorporate it into a general plan-based account of def- 
inite and indefinite noun phrases. An experimental program 
that implements individuating ~ets has already been written. 
Called BERTRAND, this program interprets a small subset of 
English statements, and stores the information in its database, 
which it then uses to answer questions. Individuating sets are 
represented by an equivalence relation that holds among refer- 
ring expressions: two referring expressions, R1 and R2, belong 
to the same individuating set if, according to the information 
interpreted so far, RI and R 2 denote the same object. In con- 
strueting individuating sets, BERTRAND uses a combination 
of logical and pragmatic strategies. The logical strategy ex- 
ploits the fact that the relation "denote the same object" is 
symmetric, transitive, and closed under substitution. Thus, it 
189 
can be concluded that two referring expressions, RI and Rz, 
denote the same object (belong to the same individuating set) 
in one of the following ways: 5 
1. Directly, when the statement "Rt is Rz ~ (or "R2 is RI ~) 
has been asserted. 
2. Recursively using transitivity -- i.e., when, for a referring 
expression Rs, it can be shown that Rl and Rs, as well as 
Rs and Rz, belong to the same individuating set. 
3. Recursively using substitution -- i.e., when Rl and Rz are 
identical, except that Rl contains a referring expression 
subRl exactly where Rz contains a referring expression 
subRz, and 8ubRl and subR2 belong to the same individ- 
uating set. 
Note that, in the logical strategy, it is tacitly assumed that 
the relation of denoting the same object always holds between 
two identical tokens of referring expressions. This is obviously 
too strong an assumption for any realistic discourse: for ex- 
ample, two utterances of "The man" may very well denote two 
different people. On the other hand, the logical strategy fails 
to capture cases in which it is implied (although never actu- 
ally asserted) that two distinct referring expressions denote the 
same thing. For example, "I met Marvin Maxwell yesterday. 
The man is utterly insane! ~ 
To compensate for these weaknesses, BERTRAND uses a 
strategy based on Grosz's notion of ffocus stack" \[8,10\]. In 
conceptual terms (and without going into details), it works as 
follows: a stack of individuating sets, representing objects that 
are "in focus," is maintained throughout the "conversation." 
When a new referring expression is interpreted, it is trans- 
formed into an open sentence D(z) with a single free variable 
z. s An individuating set I is said to subsume an open sentence 
S if S can be derived from I. The first individuating set in the 
focus stack to subsume D(z) represents the object denoted by 
the new referring expression. This solves the aforementioned 
problems: two occurrences of the same referring expression 
are considered as denoting the same object only if both are 
subsumed by the same individuating set in the focus stack, 
and two distinct referring expressions may still be considered 
as denoting the same object even though the logical strategy 
failed to show this, provided that both are subsumed by the 
same individuating set. 
Once the concept of an individuating set has been imple- 
mented, referring intentions can be represented as intentions 
to activate appropriate subsets of individuating sets. For ex- 
ample, the intention to use a conversationally relevant descrip- 
tion can be represented as the plan to activate a subset of an 
individuating set that contains the term associated with the 
description. This is the topic of a current joint research effort 
with D. Appelt \[2\] to investigate the interaction that takes 
place between individuating sets and Appelt's four types of 
SWhat belongs to an individuating set, of course, is not a referring 
expression but the logical structure associated with it. For the sake of 
simplicity, however, I do not make this distinction here. 
6For example, ~The man from the city by the bay ~ is transformed into 
Man(a:)&From(z, Xi) 
where Xi is an "internal symbol" associated with Clty(y)&By(y,Xi) , 
and )(j is associated with Bay(z). 
concept activation actions \[1\]. The next stage in the devel- 
opment of BERTRAND -- the implementation of referring 
intentions -- will be based on this research. In the final stage, 
individuating sets and referring intentions will be used to gen- 
erate actual referring expressions. 
ACKNOWLEDGMENTS 
This research was supported by the National Science Founda- 
tion under Grant DCR-8407238. I am very grateful to Doug 
Appelt and Barbara Grosz for detailed comments on earlier 
drafts, as well as to memhers of the Discourse, Intention and 
Action seminar at the Center for the Study of Language and 
Information for stimulating discussions of related issues. 
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