Towards an Account of Extraposition in HPSG* 
Frank Keller 
Centre for Cognitive Science 
University of Edinburgh 
2 Buccleuch Place, Edinburgh EH8 9LW, UK 
keller@cogsci, ed. ac. uk 
Abstract 
This paper investigates the syntax of 
extraposition in the HPSG framework. 
We present English and German data 
(partly taken from corpora), and provide 
an analysis using a nonlocal dependency 
and lexical rules. The condition for bind- 
ing the dependency is formulated rela- 
tive to the antecedent of the extraposed 
phrase, which entails that no fixed site 
for extraposition exists. Our account al- 
lows to explains the interaction of extra- 
position with fronting and coordination, 
and predicts constraints on multiple ex- 
traposition. 
1 The Data 
1.1 Extraposition of S and PP 
In English, phrases can be extraposed, i.e., dislo- 
cated to the right boundary of a sentence. This 
phenomenon can be observed with adjuncts, such 
as relative clauses or PPs in (1)-(3), as well as 
with sentential and prepositional complements as 
in (4)-(6): 1 
(1) An entirely new band rings today at Great 
Torrington, \[several of whom are members of 
the congregation\]. (UP) 
*Thanks go to Anette Frank, Tibor Kiss, Jonas 
Kuhn, Kai Lebeth, and Stefan Miiller for comments 
and suggestions in connection with the research re- 
ported here. Part of the work was carried out as part 
of the Verbmobil Project while the author stayed at 
the Institute for Logic and Linguistics, IBM Germany, 
Heidelberg. 
1Extraposition data was acquired from the fol- 
lowing corpora: UPenn Treebank (UP), London- 
Lund Corpus (LL), Stuttgart Newspaper Cor- 
pus (STZ). Other examples were taken from Culi- 
cover/Rochemont 1990 (CR), Gu~ron 1980 (CR), 
Haider 1994 (Hal), Nerbonne 1994 (Net), and 
Wiltschko 1994 (Wil). 
(2) Nobody must live here \[who is earning more 
than twenty pounds a week\]. (LL) 
(3) A man came into the room \[with blond hair\]. 
(CR) 
(4) There is very great public concern in Great 
Britain today (...) \[whether the punish- 
ments which the courts are empowered to 
impose are adequate\]. (LL) 
(5) Extensive and intensive enquiries have been 
made \[into whether this fear of this penalty 
in fact deters people from murdering\]. (LL) 
(6) I don't see much argument myself any longer 
\[against differential rents\]. (LL) 
The antecedent (the category from which the dis- 
located element is extraposed) is a noun in these 
cases. Languages in which the right VP bound- 
ary is clearly marked (as e.g. by the non-finite 
verb in verb-second languages) can provide evi- 
dence for extraposition with verbal antecedents. 
Cf. the following German data, which include the 
extraposition of adjuncts in (7) and (8), and that 
of complements in (9) and (I0). 
(7) In der Nacht hatte es Tote gegeben \[in 
in the night had there victims been in 
Moskau (...)\]. (STZ) 
Moscow 
(8) Er hat den Nerv deutscher Nachkriegs- 
he has the nerve of-German post-war 
geschichte getroffen \[mit seiner Roman- 
history hit with his novel 
Triologie (...)\]. (STZ) 
trilogy 
(9) Abet es wurde 5ffentlich aufmerksam 
but it was publicly attention 
gemacht \[auf eine prek~ire Situation\]. (STZ) 
called to a delicate situation 
(10) Er habe Schipke gesagt, \[dai\] man nicht mit 
he have Schipke said that one not with 
Eiern werfen diirfe, schon gar nicht auf 
eggs throw be-allowed, PART PARTnot at 
den Bundeskanzler\]. (STZ) 
the chancellor 
301 
But also in English, we find evidence for extrapo- 
sition from VP if we assume that adjuncts adjoin 
to the VP, and hence by default have to follow VP 
complements: 
(11) Florida National said yesterday \[that it re- 
mains committed to the merger\]. (UP) 
(12) Were hearing a lot these days \[about selling 
abroad, about the importance of Britain ex- 
porting abroad\]. (LL) 
1.2 Multiple Extraposition 
It is possible to have more than one extraposed 
phrase, as shown in (13) and (14): 2 
(13) A man -i -j came in \[with blond halr\]i \[who 
was smiling\]j. 
(14) A paper _i _j just came out \[which talks 
about extraposition\]i \[which you might be 
interested in\]j. 
In these examples, both extraposed elements are 
associated with the same antecedent. We observe 
that the serialization for multiple extraposed el- 
ements matters for PPs, but not for relative 
clauses: 
(15)*A man _i _j came in \[who was smiling\]j 
\[with blond hair\]i. 
(16) A paper -i -j just came out \[which you 
might be interested in\]/ \[which talks about 
extraposition\]i. 
We find a different pattern for multiple extraposi- 
tion involving distinct antecedents: 
(17) Its struck a grammarian _j last month 
• \[who analyzed it\]j \[that this clause is 
grammatical\]i. (Hal) 
(18)*Iti struck a grammarian _j last month \[that 
this clause is grammatical\]~ \[who analyzed 
it\]j. (Hal) 
(19) No one _i puts things _j in the sink \[that 
would block it\]j \[who wants to go on being a 
friend of mine\]/. (Gue) 
(20)*No one _i puts things _j in the sink \[who 
wants to go on being a friend of mine\]i \[that 
would block it\]j. (Gue) 
It is plausible to assume that multiple extraposi- 
tion with distinct antecedents is subject to a nest- 
ing requirement: The first extraposed phrase 
has to be associated with the last antecedent, the 
second one to the next-to-last antecedent, etc. 
Both types of constraints also apply for German, 
cf. Wiltschko (1994), who provides extensive ev- 
idence for the nesting requirement, including the 
:We use a trace-like notation to indicate the de- 
pendencies with extraposition and fronting phenom- 
ena. However, our account of extraposition involves 
no traces, cf. below. 
following data: 
(21) weil das Argument -i einen Mann _j 
because the argument a man 
anfgeregt hat, \[der das Fest besuchte\]j \[daft 
upset has who the party visited that 
Ranchen ungesund ist\]i. (Wil) 
smoking unhealthy is 
(22)*well das Argument _i einen Mann _j 
aufgeregt hat, \[daft Rauchen ungesund ist\]i, 
\[der das Fest besuchte\]j (Wil) 
1.3 Extraposition and Fronting 
The constraint of frozenness to further ex- 
traction, which states that no dislocation is pos- 
sible out of an extraposed phrase, is widely ac- 
cepted in the literature. The contrast between (23) 
and (24) illustrates this restriction: 
(23) Whoi did you see a picture of _i in the 
newspaper? 
(24)*Whoi did you see a picture in the newspaper 
of _~? 
Although this constraint seems to be valid for En- 
glish, it is possible in German to have fronting of 
material from an extraposed phrase: 3 
(25) Weni hast du geglaubt, daft Maria _~ 
who have you believed that Maria 
gekfiftt hat? (Wil) 
kissed has 
(26) \[Die Maria\]i hat Peter einem Mann _j 
the Maria has Peter to-a man 
gesagt, \[den er kannte\]j \[daft er -i gekiiftt 
said who he knew that he kissed 
hat\]. (Wil) 
has 
On the other hand, we can also observe extrapo- 
sition from fronted phrases, as (27) and (28) show 
for fronted subjects and objects, respectively. 
(27) \[Ein Buch -j\]i hat er -i geschrieben \[das 
a book has he written which 
ihn weltberiihmt gemacht hat\]j. 
him world-famous made has. 
(28) \[Ein Buch _j\]i wa~.-i erschienen, \[das ihn 
a book had appeared which him 
weltberiihmt gemacht hat\]j. 
world-famous made has. 
We find similar data with extraposition from 
fronted objects in English: 
(29) \[Which book -j\]i did she write -i last year 
\[that takes only two hours to read\]j? 
(30) \[Which woman -j\]i did he meet -i yesterday 
\[from the south of France\]j? 
Therefore, we conclude that the phrase struc- 
ture for extraposition cannot involve a hierarchi- 
aThese examples are less acceptable to speakers of 
northern variants of German. 
302 
cal constraint which states that extraposed ele- 
ments are generally higher than fronted ones or 
vice versa. This is confirmed by the observation 
that fronted elements can be involved in multiple 
extraposition as in (26). Our analysis reflects this 
by avoiding the stipulation of a fixed location for 
extraposition. 
1.4 Islands and Boundedness 
Another common assumption is that extraposition 
is not subject to the islands constraints that 
hold for extraction to the left. The contrast be- 
tween (3) and (31) makes clear that subjects are 
boundaries for fronting, but not for extraposition: 
(31)* \[With what color hair\]i did a man -i come 
into the room? (CR) 
Further, the restriction of upward bounded° 
hess applies to extraposition, i.e., in contrast to 
fronting, extraposition may not cross the sentence 
boundary: 
(32) Whoi did Mary say \[s that John saw a pic- 
ture of_i in the newspaper\]? (CR) 
(33)*It was believed \[sthat John saw a picture 
-i in the newspaper by everyone\] \[of his 
brother\]~. (CR) 
We take both constraints as evidence that extra- 
position is different from fronting and should be 
handled using a separate nonlocal feature. 
2 An HPSG Account 
2.1 Nonlocal Dependencies 
We treat extraposition as a nonlocal dependency 
and introduce a new nonlocal feature EXTRA to 
establish the connection between an extraposed 
element and its antecedent. 4 A lexical rule is 
employed which removes prepositional or verbal 
complements from the SUBCAT list and introduces 
them into the EXTRA set: 
Complement Extraposition Lexical Rule (CELR) 
\[SUBCAT \[!\] ~ \[\] \] LNONLOCI,N~RIEXTRA \[\] U(\[\] }\] 
A similar rule is used to introduce adjuncts into 
EXTRA: 5 
4We have to point out that the use of a nonlocal 
feature is not crucial to our analysis (as extraposition 
cannot cross the sentence boundary), but was chosen 
for technical convenience. Defining EXTRA in this way, 
we can rely on the Nonlocal Feature Principle for per- 
colation; no additional mechanism is required. 
5Note that this is a recursive lexical rule, which 
Adjunct Extraposition Lexical Rule (AELR) 
"r,oc \[\] ICATIHEAD nou,~ Vverb\] I NONLOCIINHERIEXTRA \[\] \] 
L oo Tr  JJJ 
Note that the semantic contribution of the adjunct 
(standardly dealt with by the Semantics Princi- 
ple) is incorporated into this lexical rule. The shar- 
ing \[\] states that the CONT-value of the output 
is identical with the CONT of the extraposed ele- 
ment, which in turn incorporates the semantics of 
the input via the sharing \[\]. 
2.2 Periphery Marking 
Intuitively, our approach to the phrase structure 
of extraposition can be formulated as follows: 
An extraposed constituent has to be bound on 
top of a phrase that introduces intervening mate- 
rial between the extraposed constituent and its 
antecedent. 6 Since this constraint on the bind- 
ing of an extraposed element is relative to its an- 
tecedent, we have no fixed site for extraposition, 
which explains the observed interaction between 
extraposition and fronting. It also entails a nesting 
requirement for multiple extraposition, as it trig- 
gers distinct binding sites for extraposition from 
distinct antecedents: The binding site reflects the 
relative position of the antecedent, b-hrthermore, 
we avoid spurious ambiguities which have been 
problematic for previous accounts/ 
Our requirement for EXTRA binding can be for- 
mulated in HPSG using the notion of periphery, 
which is defined for phrases containing an EXTRA 
element: A phrase has a left periphery iff it con- 
tains an EXTRA element which is inherited from 
(a) its phrasal rightmost daughter or (b) from its 
lexical head. Otherwise, the phrase has a right 
periphery, and EXTRA elements can be bound on 
is rather unusual in standard HPSG. But cf. van No- 
ord/Bouma (1994) who show some other cases where 
recursive lexical rules are useful and deal with pro- 
cessing issues as well. 
6Our analysis is inspired by the Locality Con- 
straint for Identification (LCI) which Wiltschko 
(1994) proposes to account for extraposition in a GB 
framework. The LCI requires that an extraposed ele- 
ment is adjoined at the first maximal projection which 
dominates its antecedent. 
ZCf. Keller 1994, where we posited the S node as 
a fixed site for the binding of extraposed elements. 
Apart from leading to spurious ambiguities, this as- 
sumption is incompatible with the coordination data 
given in sec. 3.1. 
303 
top of it. 
In case (a), no material exists to the right of the 
extraposed element which could intervene between 
it and an antecedent. In case (b), the EXTRA el- 
ement originates directly from a lexical head and 
would be indistinguishable from a non-extraposed 
complement or adjunct if bound immediately. In- 
tuitively, in both cases, the EXTRA element has to 
be bound further up the tree after it has found 
intervening material which identifies it as extra- 
posed. 
Our periphery definition entails that in a sentence 
which contain more than one projection with a 
right periphery, multiple locations for extraposi- 
tion exist correspondingly. If a sentence contains 
no projection with a right periphery, no extrapo- 
sition is possible. 
To formalize the notion of periphery, we introduce 
a new feature PERIPHERY (PER), which is located 
under LOCAL. Its value is of type periphery, de- 
fined as follows: 
(34) Partition of periphery: extra, non-extra 
Partition of non-extra: left, right 
The correct instantiation of PER is guaranteed by 
the following condition: 
(35) Periphery Marking Condition (PMC) 
A headed phrase is marked \[PER left\] if 
it has a daughter D with a non-empty 
INHERIEXTRA set, and D is 
a. the rightmost daughter and phrasal; or 
b. the head daughter and lexical and mark- 
ed \[PER left\]. 
Note that (35b) allows for periphery marking to 
be specified lexically. We will return to this in 
sec. 2.6, where we formulate a parochial restric- 
tion for German. For English, however, we assume 
that all lexical entries are marked \[PER left\]. 
2.3 Phrase Structure 
To implement the binding of extraposed elements, 
we introduce an additional immediate dominance 
schema, which draws on a new subtype of head- 
struc called head-extra-struc bearing the feature 
EXTRA-DTRS (taking a list of sign). As the binding 
of extraposed elements is only possible at the right 
periphery of a phrase, the head-extra schema spec- 
ifies its head daughter as \[PEa right\] and marks its 
mother node as \[PEa extra\] (the latter is needed 
for the treatment of adjuncts, el. see. 2.5): s 
SHere loc(x) denotes a function which takes as x a 
list of sign and returns a set of loc containing the boc 
values of the elements of x. 
Head-Extra Schema 
rLoolPER e ,ro 1 
LEXTRA-DTRS I~ 
Note that the specification \[INHERIEXTRA { }\] re- 
quires all members of EXTRA to be bound at the 
same level. This ensures that extraposed elements 
originating from the same phrase axe sisters, and 
hence can be ordered by LPCs. We use LPCs to 
account for multiple extraposition from the same 
antecedent (cf. the data in (13)-(16)): 
(36) a. H < E 
b. E \[HEAD prep\] < E \[HEAD verb V rel\] 
The constraint in (36a) orders the EXTRA-DTRS 
(E) after the HEAD-DTR (H). With regard to the 
EXTRA-DTRS, PPs have to precede sentences or 
relative clauses, as stated in (36b). 
2.4 Examples 
The (simplified) tree structures for (6) and (3) are 
given in (37) and (38): 
(37) S 
1 VP \[~HIEX {~}J AP aghast DR 
any longer J PER left \] 
see NP~ El} 
no argument 
(38) 
r51NP 
S\[PERextra\] 
\[I~HIEX {\[i\] }\] \[i\]PP 
\[INHfEX {\[\]}\] "J with red hair 
a man came into the room 
304 
2.5 Adjuncts 
The phrase structure for extraposition outlined 
so far has to be constrained further, since it al- 
lows adjuncts to adjoin higher than extraposed 
elements, which is clearly wrong. Cf. the following 
examples with extraposition from NP: 
(39)* An entirely new band rings today, \[several of 
whom are members of the congregation\] at 
Great Torrington. 
We conclude that the application of the head- 
adjunct schema has to be disallowed on top of 
a head-extra structure. This can be achieved 
straightforwardly by specifying adjuncts as 
\[MODILOClPER non-extra\]. 
2.6 Extraposition from VP 
The AELR has to be restricted language- 
specifically to account corectly for extraposition 
from VP: 
English has a head-initial VP, therefore the right 
periphery of the VP cannot be formed by the 
verb, but is provided by VP adjuncts (adverbs and 
PPs). As a consequence, extraposed VP adjuncts 
cannot be distinguished from VP adjuncts in base 
position, which is clearly undesirable. Therefore, 
we restrict the AELR to nouns on the input side, 
which disallows adjunct extraposition from VP 
and hence avoids spurious ambiguities. 
In German, in contrast, the AELR can apply 
in full generality. German has a head-final VP, 
which entails that a verb in final position can form 
the right periphery of a phrase, making extrapo- 
sition of VP adjuncts and complements possible. 
We exploit of the lexical constraint in the PMC 
in (35b) to allow the binding of extraposed ele- 
ments on top of verbs in final position, which we 
assume with Pollard (1990) to be marked \[INV --\]. 
We can therefore formulate the following lexical 
requirement:9 
(40) \[INV --\] ~ \[PER right\] 
All other lexical entries are marked \[PER left\], and 
hence cannot introduce a right periphery. 
2.7 Fronting 
To account for the differences between English and 
German concerning the fronting from extraposed 
elements (cf. (24) vs. (25)) we restrict the head- 
extra schema as follows: 
For English we assume that both INHERISLASH 
and INHER\[EXTRA have to be empty for all ele- 
ments of EXTRA-DTRS. This guarantees that nei- 
9A similar rule has to be formulated for verbs with 
separable prefixes, where the prefix marks the right 
periphery. 
ther fronting nor further extraposition is possible 
from extraposed phrases. 
For German we assume that only INHERIEXTRA 
has to be empty for all elements of EXTRA-DTRS. 
Therefore, fronting but not extraposition is al- 
lowed from extraposed phrases. 
3 Predictions and Generalizations 
3.1 Extraposition and Coordination 
The head-extra schema together with the PMC 
has the consequence that elements extraposed 
from objects are bound at VP level, whereas extra- 
position from subjects involves binding at S level, 
as illustrated in (37) and (38). This is confirmed 
by the following coordination data, which shows 
that an element which is extraposed form the sub- 
ject cannot occur at VP level: 
(41) Is Nobody must live here and benefit from 
income support\] \[who is earning more than 
twenty pounds a week\]. 
(42)*Nobody must \[vplive here \]\[who is earn- 
ing more than twenty pounds a week\] and 
\[vP benefit from income support\]. 
We find similar data for German, where the sub- 
ject of a finite clause is related to the S projec- 
tion via a SLASH dependency, and therefore the 
head-extra schema applies on top of the head-filler 
schema: 
(43) Is, Die Behauptung iiberrraschte reich und 
the claim surprised me and 
erstaunte Maria\], \[dab Rauchen ung. ist\]. 
puzzled Maria that smoking unh. is 
(44)*Die Behauptung Is fiberrraschte mich\] \[da~ 
Rauchen ungesund ist\] und \[s erstaunte 
Maria\]. 
The Coordination Principle (Pollard/Sag 
1994: 202) requires for coordinate structures 
that the CAT and NONLOC value of each conjunct 
daughter is identical to that of the mother. If we 
add the assumption that the mother is always 
marked as \[PER right\], 1° then the following data 
with split antecedents can be accounted for: 
(45) Ein Mann ~iut3erte die Behauptung und eine 
a man uttered the claim and a 
Frau leugnete die Tatsache daft Rauchen 
woman denied the fact that smoking 
ungesund ist. 
unhealthy is. 
Here EXTRA is shared between the conjuncts and 
bound at S level. Parallel examples exist for En- 
glish: 
1°Note that this is possible as the PMC is valid only 
for headed structures. We also draw on the fact that 
PER is a LOCAL feature. 
305 
(46) A man came in and a woman went out who 
knew each other well. (CR) 
3.2 NP-internal Extraposition 
We also find evidence for extraposed phases within 
NPs, i.e., examples in which adjuncts precede 
complements: 
(47) In \[NP an interview \[published yesterday\] 
\[with the Los Angeles Daily News\]\], Mr. Sim- 
mons said: "Lockheed is actually just a de- 
coy. (...)" (uP) 
(48) "The question" at \[NP a closed-door meeting 
\[K mart is scheduled to hold today\] \[with an- 
alysts\]\] "will be: Why aren't we seeing better 
improvement in sales?" (UP) 
These data are not unexpected in our account, 
since we posit no fixed position for extraposition, 
and hence allow that an extraposed NP comple- 
ment is bound inside the NP itself, provided that 
an adjunct is present to mark the right periphery 
of the NP. This is the case in (47) and (48). 
3.3 VP-internal Extraposition 
Much in the same vein as with NP-internal ex- 
traposition, our account accommodates cases of 
VP-internal extraposition, which are possible with 
fronted partial VPs in German: 
(49) \[vp \[Einen Hund fiittern\], \[der Hunger hat\]\], 
a dog feed which hunger has 
wird wohl jeder diirfen. (Net) 
will PART everyone be-allowed 
(50)* Es wird wohl jeder \[vP \[einen Hund ffittern\], 
der Hunger hat\], dfirfen. (Net) 
The contrast between (49) and (50) shows that 
extraposition inside a VP is possible only if the 
VP is fronted. If we assume with Nerbonne (1994) 
that partial VPs exist in fronted position, but not 
in the matrix clause, this contrast is readily pre- 
dicted by our account. Only in fronting examples 
like (49), the VP does form a separate constituent 
and hence does exhibit the periphery marking 
needed for extraposition. 
3.4 Generalizations 
We sum up the generalizations that are captured 
by our analysis: 
(a) Relative clauses, sentences, and PPs can be 
extraposed, nouns and verbs can function as 
antecedents. These category restrictions are 
subject to crosslinguistic variation, as the the 
AELR for English shows (cf. sec. 2.6). 
(b) Both extraposition from fronted phrases and 
fronting from extraposed elements axe ac- 
counted for by our head-extra schema which 
is constrained by the PMC. In English, 
fronting from extraposed constituents is dis- 
allowed by a language-specific constraint. 
(c) The PMC also entails a nesting require- 
ment for extraposed elements with distinct 
antecedents. Extraposed elements with the 
same antecedent are bound at the same level 
and LPCs apply. For English and German, 
PPs have to precede sentential material. For 
other languages, different orderings may be 
stated. 
(d) The fact that no island constraints for extra- 
position exist follows from our use of EXTRA: 
Island restrictions are formulated for SLASH 
and hence do not apply to extraposition. 
(e) The upward boundedness of extraposition 
can be captured by stating that a sentence 
has to be \[INHERIEXTRA { }\]. 
(f) Our analysis predicts the asymmetry be- 
tween extraposition from subjects and ob- 
jects as found e.g. in coordination data. 
(g) NP-internal extraposition and extraposition 
within fronted VPs are captured without the 
assumption of any further mechanisms. 
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