ON THF. SYNTACTIC-SEMANTIC ANAT,YSIS 
OF BOUND ANAPHORA 
1WA~fred Pinkal 
Universit~t Saarbriicken, Computerlinguistik 
D-6600 Saarbriicken, Gexrp~-y 
E-Mail: pinkal@coH.uni-sb.de 
ABSTRACT 
Two well-known phenomena in the area 
of pronoun binding are considered: 
Indirect binding of pronouns by indefinite 
NPs ("donkey sentences") and surface- 
syntactic constraints on binding ("weak 
cross-over"). A common treatment is 
proposed, and general consequences for 
the relation between syntactic and 
semantic processing are discussed. It is 
argued that syntactic and semantic 
analysis must interact in a complex way, 
rather than in a simple sequential or strict 
rule-to-rule fashion. 
1. A SEMANTIC BINDING CONDITION: 
STANDARD ACCOUNT 
We start our considerations on the mecha- 
nism of pronoun binding with the ten- 
tative formulation of a semantic binding 
condition in (I): 
(I) ANP can bind pronouns in its scope 
Taken that the "scope of a NP" means the 
scope of the (generalized) quantifier the 
NP translates to, and that pronouns are 
semantically represented by individual 
variables, Binding principle (1) more or 
less directly corresponds to the conditions 
on variable binding in predicate logic, 
and therefore has a great deal of intuitive 
plausibility with it. Accordingly, it is 
explicitly or silently assumed as the basic 
principle for pronoun binding in many 
theoretical and computational approaches 
to the semantics of natural language. 
Principle (1) makes correct predictions 
for a wide range of natural language ex- 
amples (we disregard the distinction bet- 
ween reflexive and non-reflexive pro- 
nouns throughout this paper). E.g., it ex- 
plains why sentence (2) is fine, whereas 
(3) is impossible (binding is indicated in 
the usual way by co-indexing). 
(2) \[NPEvery student\]i admires hisi 
teacher 
(3) * If \[NPevery student\]i admires hisi 
teacher, hei is a fool 
2. A REVISED SEMANTIC BINDING 
CONDITION: DRT 
Binding principle (1) has turned out to be 
too restrictive. The indicated binding in 
Sentence (4), below, is fine although a book 
cannot take scope over the main clause 
where the bound pronoun occurs: It should 
not take wide scope for syntactic reasons 
(it occurs in a relative clause which is a 
clear case of an island construction), and 
if it did, the wrong semantics would result 
(globally, it functions as a universal ra- 
ther than an as an existential quantifier, 
in (4)). 
(4) Every professor who owns \[NP a book\]i 
reads iti 
This is the well-known "donkey-sentence 
problem" which motivated the DRT-style 
reformulation of natural language 
semantics (Discourse Representation 
Theory: Kamp 1981; File Change Se- 
mantics: Helm 1982). The solution that 
DRT provides for the donkey sentence 
- 45 - 
problem can be roughly outlined as 
follows: The common semantic function 
of non-anaphorical noun phrases is the 
introduction of a new discourse referent, 
which is in turn available for the binding 
of anaphoric expressions. Beyond this 
basic function, non-anaphorical noun 
phrases subdivide into genuine quanti- 
tiers (e.g., every professor), and non- 
quantificational NPs (e.g., the indefinite 
NP a book). Only the former bear scope. 
An every-NP, e.g., triggers the intro- 
duction of a complex condition of the form 
K I ~ K2, where K 1 and K 2 are sub-DRSes 
representing the restriction and the scope 
of the quantification respectively. In- 
definite NPs just contribute a new 
discourse referent (together with some 
descriptive material in terms of con- 
ditions on the discourse referent), which is 
placed in a larger structure. This larger 
structure can be the top-level DRS or some 
sub-DRS according to the sentence-inter- 
nal environment of the analyzed NP. 
Indefinite NPs do not have scope by 
themselves. It follows that Principle (1) 
cannot apply to Sentence (4), if it is taken 
literally. However, the model-theoretic 
interpretation for complex conditions is 
defined in a way that indefinite NPs 
share quantificational force and scope 
with their "host quantifier" (i.e., the 
quantificational NP whose representation 
contains the discourse referent introduced 
by the indefinite on the top-level of its 
restriction part). Accordingly, an inde- 
finite NP should observe the restrictions 
on binding imposed by that larger 
quantificational structure. Therefore, the 
original binding principle (1) must be 
replaced by something like (5). 
(5) A NP a can bind a pronoun ~ provided 
that ~ is in the scope of the host ~lantifier 
of a's discourse referent. 
Actually, the revised binding principle (5) 
permits binding in (4), whereas the 
indicated binding in (6) is excluded under 
the preferred reading where every 
professor outscopes a book, which is in 
accordance with intuitions. 
(6) * If every professor owns \[NP a book\]i, 
a student reads iti 
Standard DRT tries to give a general 
account for the constraints on anaphoric 
binding by specifying an accessibility 
relation between positions in a complex 
DRS. The formulation of the revised 
binding principle in (5) is obviously 
neither general nor precise enough to 
replace the standard DRT treatment. We 
will come back to the point in Section 4. 
3. A SYNTACTIC BINDING CONDI- 
TION 
The scope of noun phrases is not deter- 
mined by their surface syntactic position. 
(7) Every professor owns a book 
Expressed in terms of conventional 
predicate logic or generalized quantifier 
theory, Sentence (7) is ambiguous between 
a narrow-scope reading and a wide-scope 
reading of the existential NP a book. The 
former corresponds to the constituent 
structure of (7), the latter is due to a 
"delayed application" of the existential 
NP, which can be brought about by 
different syntactic and semantic 
techniques (e.g., Quantifier Raising: 
May 1985, Cooper Storage: Cooper 1983). 
Scope variation leads to an additional 
difficulty with the binding principle (1): If 
NPs (i.e., quantifier terms, on the 
Standard account) are applied in situ, 
their semantic scope precisely parallels 
their c-command domain in surface 
structure. Examples of postponed 
quantifier application disturb the 
parallelism and by that provide evidence 
that the syntactic c-command concept is 
relevant for binding in addition to the 
semantic notion of scope. 
(8) *A student of hisi admires \[NP every 
teacher\]i 
In Sentence (8), every teacher may take 
scope over the indefinite NP a student of 
h/s. That the pronoun h/s is in the scope of 
- 46 - 
the quantifier is obviously insufficient to 
license binding, which seems to be 
blocked by the fact that the object NP does 
not c-command the pronoun. This pheno- 
menon, the so-called "Weak-Crossover 
Effect", shows that the semantic principle 
(1) is too weak to properly constrain ana- 
phoric binding, and has lead to a syntactic 
binding principle the classical formu- 
lation of which is given in (9) (cf. Rein- 
hart 1983, Williams 1986). 
(9) A NP can bind pronouns in its c- 
comm~rld domain. 
As more recent theoretical work has 
shown, the c-command condition is only 
an approximation to reality (cf. Stowell 
1989). However, the precise definition of 
the c-command relation and the syntactic 
condition as a whole is not crucial for the 
argument. The important point is that 
anaphoric binding is apparently 
dependent on genuinely syntactic facts: 
The decision of whether a pronoun can be 
bound by a NP cannot be made on the basis 
of semantic information only. There are 
basically two possible ways out: On the 
one hand, one can pass the task of 
specifying anaphoric relations completely 
to syntax (this is the answer of GB 
grammarians). On the other hand, one 
can make certain portions of syntactic 
information available for semantic 
processing (proposals are made in Pol- 
lack/Pereira 1988, Latecki/Pinkal 1990). 
The choice between the two solutions 
seems to some extent to be a matter of taste: 
Plausibility reasons as well as efficiency 
considerations for natural language pro- 
cessing speak against the first solution. 
The fact that one has to import and process 
syntactic information within semantic 
interpretation seems to be a certain 
methodological drawback. I will come 
back to the question after having dis- 
cussed a further complication in the next 
section. 
4. BINDING, SYNTACTIC AND SE- 
MANTIC CONDITIONS TOGETHER 
In the last section, the phenomenon of 
scope ambiguity and its consequences for 
anaphoric binding have been considered 
on the background of the standard 
semantic framework. Obviously, a two- 
reading analysis for sentences like (7) 
must be provided in a DRT-based 
analysis, as well, although it must be 
accounted for in a slightly different way. 
The two readings of (7) do not differ in the 
relative scope order of two quantifiers. 
Rather, the difference is that on the 
narrow scope reading, the discourse 
referent introduced by a book occurs 
inside the complex condition established 
by the universal NP (its host quantifier), 
whereas on the wide-scope reading it 
occurs on the top-level of the DRS. 
Scope ambiguities are not treated in the 
original DRT version; they are difficult to 
model with procedural DRS construction 
rules that operate on surface syntactic 
structures. There is however a convenient 
and straightforward way to combine the 
DRT formalism with the technical means 
of lambda-abstraction. (10) indicates how 
representations of the NPs every professor 
and a book as partially instantiated 
DRSes can be given using lambda-ab- 
straction over predicative DRSes (The 
latter are obtained from standard DRSes 
by abstraction over a discourse referent. 
The "(9" sign in (10) is an operator which 
merges two DRSes.) 
(1o) 
x = S(x) 
professor (x) 
I Y eR(y) book (y) 
, 
One effect of this modification of DRT is 
that semantic representations can be 
constructed compositionally, in a bottom- 
up fashion. Another consequence is that 
- 47 - 
the standard techniques for delayed 
application become available in the DRT 
framework. 
Not surprisingly, we run into difficulties 
with the revised semantic binding 
condition (5) in connection with the weak 
crossover cases, as soon as we treat scope 
ambiguities in a DRT-style analysis. 
According to (5), both the standard weak 
crossover example (8) and the inverted 
donkey sentence (11) should be acceptable. 
(11) *Itsi readers admire every professor 
who writes \[NP a book\]i 
Since the discourse referent provided by a 
book takes its place at the top level of the 
restriction part of the every-NP, the in- 
definite should count as a proper ante- 
cedent for the pronoun on the reading 
where the every-NP takes wide scope over 
the whole sentence. If in addition the 
syntactic binding principle (9) is 
observed, cases like (8) and (11) are 
correctly ruled out: Neither every teacher 
in (8) nor a book in (11) c-command the 
respective pronouns. But unfortunately, 
also those cases of anaphoric binding are 
blocked which provided the original moti- 
vation for DRT, namely the donkey-sen- 
tence cases discussed above. In sentence 
(4), the antecedent NP a book definitely 
does not c-command the pronoun it. 
Examples like (8) and (11) demonstrate 
that a syntactic condition on binding has 
to be observed, also under a DRT-based 
analysis. The considerations of the last 
paragraph however show that this 
syntactic condition cannot be c-command 
between antecedent and pronoun. A modi- 
fication of the syntactic binding principle 
(9) appears to bring about the right 
predictions: It is not the antecedent which 
must c-command the pronoun, but the 
quantificational NP, the host operator of 
the antecedent's discourse referent. In (4), 
the pronoun it is in the c-command 
domain of the NP every professor who 
owns a book, whereas in (8) and (11), 
where binding is impossible, the uni- 
versal NP does not c-command the pro- 
noun. 
In (12), a revised version of the syntactic 
principle (9) is proposed. 
(12) A NP a can bind a pronoun ~ provided 
that ~ is in the c~ommand domain of the 
host q, lantifier of a's discourse referent. 
The revised principles (5) and (12) to- 
gether capture the complex conditions on 
binding in donkey sentences. They are 
not general enough, however, for they do 
not say anything about the binding 
conditions on indefinites which are not 
associated to the restriction of a genuine 
quantifier term. In the following, a more 
dynamic formulation of the binding rule 
is given, which has larger coverage and 
contains the interaction of quantification 
and indefinites in donkey sentences as a 
special case. 
We assume that the immediate effect of the 
analysis of a pronoun is just the 
introduction of a discourse referent, which 
is also marked as a candidate for 
binding. Each semantic representation 
contains together with the DRS infor- 
mation about the unbound pronominal 
discourse referents. Binding can take 
place whenever a NP denotation (quanti- 
ficational or indefinite) is applied to a 
predicative DRS, according to (13). 
(13) When the denotation a of a noun 
phrase A is applied to a predicative DRS 
XuK, any tol~level discourse referent of a 
can bind an unbound pronominal dis- 
Course referent of K, provided that the 
respective pronoun is in the c~ommRnd 
domain of A. 
Rule (13) also accounts for the different 
status of (14) and (15), where (15) is ex- 
cluded by the syntactic constraint. 
(14) \[NPA teacher\]i admires a student ofhisi 
(15) *A student ofhisi admires \[NP a 
teacher\]i 
- 48 - 
5. A GENERAL RESULT FOR SYN- 
TACTIC-SEMANTIC PROCESSING 
The results of the last section have 
consequences for the over-all view of 
syntactic-semantic processing of natural- 
language sentences containing anaphoric 
pronouns. The revised binding principle 
(12) relates the pronoun ~ and its 
antecedent cz indirectly, by making refe- 
rence to the quantifier term 7 which even- 
tually contains the discourse referent of 
the antecedent NP. Now, the relation 
between the pronoun ~ and the host quanti- 
fier 7 is a syntactic one, whereas the 
relation between 7 and the antecedent a is 
a semantic relation: Up to which position 
in the DRS the discourse referent 
eventually percolates will only turn out, 
when the corresponding portion of 
semantic analysis is done. 
This means that the decision between the 
two ways of specifying anaphoric rela- 
tions which were mentioned at the end of 
Section 3 is no longer a matter of taste: 
The linguistic data force a choice in favor 
of the second alternative. 
The possible anaphoric relations in a 
sentence cannot be specified by the 
syntactic component only: Some amount 
of semantic processing must precede the c- 
command check (in order to know which 
constituents are to be checked). And they 
cannot be specified by the semantic 
component only, since there are obviously 
surface-syntactic constraints on binding. 
Therefore the strict sequential model of 
syntactic and semantic processing: co- 
indexing in the syntactic component and 
strictly deterministic semantic inter- 
pretation, which is explicitly or implicitly 
favored by adherents of the Government- 
and-Binding approach, cannot be main- 
tained (if we disregard the theoretically 
possible, but highly non-deterministic 
method of random indexing and semantic 
filtering). Also, anaphora cannot be 
treated as a matter of syntax-free se- 
mantics. Syntax and semantics must 
interact in a non-trivial way in order to 
determine what an admissible antecedent 
for an anaphoric pronoun is. 
6. IMPLEMENTATION 
The described interaction between syntax 
and semantics suggests a processing 
model with independent, but freely inter- 
acting modules in the spirit of principle- 
based parsing. Actually, an implemen- 
tation of a principle-based NL system with 
a semantic module covering the pheno- 
mena discussed in this paper in in 
preparation. It will basically be an ex- 
tension of the system described in Millies 
(1990). 
A more conventional system for DRT- 
based syntactic-semantic analysis that 
generates admissible scope readings has 
been implemented in Quintus Prolog at 
the University of Hamburg, in a DCG 
style grammar system. A declarative 
version of DRT is used, which bears 
certain similarities to the one described in 
Zeevat (1989). Semantic interpretation is 
carried out in parallel to syntactic 
analysis. Scope readings are produced 
using a modified version of Cooper 
Storage, which is equivalent in its results 
to Nested Cooper Storage (Keller 1988) and 
the Hobbs-Shieber-Algorithm (Hobbs/ 
Shieber 1987), but employs an efficient 
indexing technique to check violations of 
free variable constraint and syntactic 
island constraints. 
An extension of the system which checks 
the admissibility of anaphoric relations is 
under work at Saarbriicken University. c- 
command is checked by another version 
of the above-mentioned indexing tech- 
nique (described in Latecki 1990) Rele- 
vant syntactic information is imported 
into semantics by attaching index sets to 
term phrases in the storage; it is activated 
at the time of the (delayed) application of 
the quantifier term. The system for 
treating quantifier scope as well as its 
extension to anaphoric binding are 
described in Latecki/Pinkal (1990). 
- 49 - 
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