Toward a Redefinition of Yea/No Questions 
Julia Hirschberg 
Department of Computer and Information Science 
Moore School/D0 
University of Pennsylvania 
Philadelphia, PA 19104 
ABSTRACT 
While both theoretical and empirical studies of question- 
answering have revealed the inadequacy of traditional definitions 
of Ve*-no questions (YNQs), little progress has been made 
toward a more satisfactory redefinition. This paper reviews the 
limitations of several proposed revisions. It proposes a new 
definition of YNQs baaed upon research on a type of 
conversational irnpIieature, termed here setdar 
imp/ie,,ture, that helps define appropriate responses to YNQs. 
By representing YNQs as sealer qtteriee it is possible to support 
a wider variety of system anti user responses in a principled way. 
I INTRODUCTION 
If natural language interfaces to question-answering systems are 
to support a broad range of responses to user queries, the way 
these systems represent queries for response retrieval should be 
reexamined. Theorists of question-answering commonly define 
questions in terms of the set of all their possible \[true) answers. 
Traditionally, they have defined t/us-no quesgiofts (YNQs) as 
propositional questions (?P) or as a special type of 
alternative question (?P V ?Q), in which the second alternative 
is simply the negation of the fir.~t (?P V ?"P). So 'Does Mary like 
skiing?' would be represented as flikr(lffary,skling) or 
?like(Alary.okiing) V "~-Iikt(Mary, skiing) and the range of 
appropriate responses wouhl be gee, no and, possibly, unknown. 
• " ilowever, both theoretleal wnrk and empirical studies of naturally 
occurring question-answer exchanges have shown this approach to 
be inadequate: ?~s, .o. and unknown form only a small portion of 
the set ¢,f all appropriate responses to a YNQ. Furthermore, for 
some YNQ's. none of these simple direct responses alone i~ 
appropri:,te. 
While it is widely recognized (llobbs, 1979, Pollack, 1982} that 
indirect resp.nses I to YNQs represent an important option for 
respondents in natural discourse, standard theories of question- 
answering have n,~t been revised accordiugly. A practical 
COllsPquence surface~ when attempts are made t.o support indirect 
responses to YNQs computationally. For lack of alternative 
representations, question-answering systems which would permit 
indirect responses must still represent YNQs as if the direct 
respons-s were the 'norm', and then resort to ad hoe manipulations 
to generate second-class 'indirect' responses, thus perpetuating an 
asymmetric distinction between 'direct' and 'indirect' responses. 
However. resea.'h under way on how a type of generalized 
conversational implieatttre, termed here scalar 
irrtplieature, can be used to guide the generation and 
iaterpretion of indirect respt,nses to YNQs sugges/,s a revi~ed 
representation fi)r YNQs which scrotums)dates a wide variety of 
responses in a uniform way. 
II CURRENT REPRESENTATIONS OF YNQ, S 
Among st:~ad:,rd accounts of ¥NQs, I-lintikka's (l.lh:tik.~a, 197~) 
is one of the shnl)lest and mo~t widely accepted, c~.,mbinh~g the 
llndirect r~sponses to YNQs tr~ defined h~:re as responses other than lltR, 
n0, or some expression of ignorance. 
concepts of YNQ" as pn,positional question " and as alternative 
question; as such, it will be used below to represent traditional 
approaches in general. To define attswerhood, the conditions 
under which a response eonnts as an answer to a natural-language 
query, Hintikka divides qneriq~s into two parts: an imperative or 
optaGve operator {\[). roughly expressing 'bri,g it about that', and 
a daesideratu~,n, a specification of the epistemie state a questhmer 
desires. For Hintikka, a YNQ is a ~peciai case of alterna(Jve 
question in which the negative alternative 'or not P' has been 
suppressed. So the desideratum of a YNQ is of the f¢~rm (\[ know 
thai P) V {I kin, u, that #t~3+P}. where net-l- indicates the 
negation-fi)rming process. 'Does Mary like skiing?' thus has a.s its 
desideratum I know that ,~htrg li\];e.* skiing or I kno~ ihat Aiary 
does not like skiing, or, more concisely, fK~Jike{Marg, skling) V 
Ks~likc{'Marll, ekiing), where K S is the epistemic representatitm of 
'S knows that'. The full sense of the query is then 'Bring it aboot 
that 1 know that Mary likes skiing or that I know that Mary does 
not like skiing', which can be represented by ! \[KsP V K.~',P). 
Possible resp.nses are simply {P,-,P}, or {yes,no). 
A. tI_~othesls Confirmation 
Bolingcr (Boliuger, 1978) has called such interpretations into 
question by showing that YNQs may have very different meanings 
from their alternatlve-questioa counterparts; they also have more 
restricted paraphrase and intonation patterns. In 13oliuger's view 
the term I/US-no qtterl/ has hypnolized scholars into a.ssurrling 
that, simply because a class of question can be answered by a 2us 
or no, the~ altern:ttives are critcrial, and every YNQ is intended 
to elicit, one or the other. He proposes instead that YNQs be 
viewed as hypotheses put forward for confirmation, arncadmenL or 
diseonfirnladon - in any degree. Thus, in Bolinger's exampie (l), 
the 
(1) Q: Do you like llonolnlu? 
R: Just a little. 
questioner (Q)'s hypothesis 'you like tloaoh, iu' is amended by ~he 
respondent (R) in a re.-ponse v, hich is neither .t, es n,~r no bnt 
somewhere in between. In his example (2), Q's hypothesis 'it is 
(2) Q: Is it difficult? 
R: It's imposeS'de. 
difficult' is confirmed by R's as,ertion of a more positive resi~onse 
than a simple go.;. 
While Bolingcr makes a good ca'.:.e for the inadequacy of sttmdard 
views of YNQs, the revisi,m hv I)mposes is itself :,~, \]i,tited. '~t',~ 
imp~,~ible', in (2). d.',e:; n:,.'e than simply pr~'-,..t a strong 
affirmation of the hypoth,'~is 'it is dilficult' - it Frovid~ new :'.rid 
unrequested though perlit..nt inr,,r.tati.n. In fact, 'str,mg 
affirmation' might better t)e provided by a respon.-e -.uch as '1 am 
absolutely sure it's difficult' than by "he response he suggests. And 
ther,~ are equally appropriate responses to the queries in (l) and {2) 
that are not easily explained in terms of degree of hypotl~esis 
confirmatit,n, u.~ shown iu (3) and (4). 
/48 
(:~;) Q: 1),, you like ! h,,a.hllu? 
a. R: I don't like llawaii. 
b. R: I lik~- Ililo. 
(4} t~: Is it dif~'icult? 
a. l,': It could be. 
b. It: Mike says so. 
Finally, l~.ii~ger does not propose a representatiozt to 
accommodate hi~ hy~,~,the~is-confirmation model. 
B. Fo~oesed YNf~.~ 
Similarly, Ki,'fer (Kid,for, 19~;0) points out evidence for the 
inadt,quacy of the standard view of YNQs, but proposes no unified 
sohrti.n. In a stt~dy of the indirect speech acts that may be 
p~.rh~rm,'d I,? "(NQ~, h," nc~le~ that certain YNQs, which he terms 
.focussed YTVQs, aetu:dly function as v,h-queslions. Focussed 
YNQs I'¢,r Kit'f,'r are YNQs that are marked in some way 
(:~l)parenlly by sire:.~ i to il~di,.ate a background aasuntption 
which Q and l{ typic:ally share. For example, (Sa) is not a 
focussed YNQ while {Y~bHY, d ) are. While any of the four may be 
auswrted with 9~,~ or 
a. 1.~ John h,aving for .~tockholm tomorrow? 
b. Is .Mhn leaving for Stockholm TOMORROW? 
c. Is John h.aviug for STOCKIR~I.M tomorr,~w? 
d. \[s JOIIN leaving fi~r St~wkh.~dm tom~)rrow? 
no, ii is also po~.ii,le that, if Q a~ks (,Sb). she want~ R to answer 
the question 'When is Johi! leaving for Stockholm?'; if she a.,;ks (Se) 
she may want to know 'Where is John going tomorrow?'; and if 
she asks (Sd) she may want to know 'Who is leaving for Stockhohn 
tomorrow?" Titus a f,~cussed YNQ resemhles the wh-question that 
might be formed by replacing the focussed element in the 
desideratum with a corresponding Pro-element. In Kiefer's 
analysis, only one eh't~ent can he focussed, so resl~mses such as 
'lie's leaving for Paris Thursday' will not be accommodated. 
Although Kiefer does not propose a representation for focugsed 
YNQs, a di..:j,nc! resembling the desideratum of a wh-question 
might I,e added to the traditional representation to areommodate 
his third :tlterna|ive: for (5d} this might take the form 'Is John 
leaving for Stoekhohn tomorrow, or, if not, who is?' or, in 
Hintikka's notation, 
! KQleaving(.Iohn,Stockholm,tomorrow) V 
Kq-leav ing{.Ioh n,Stoek h-Ira,tomorrow) V 
3x Kqleav ing(x,Stoek holm,tomorrow). 
This represenl.atiou reflects another problem posed by Kiefer's 
analysis: the third disjunet is appropriate only when the second 
also is and not when the direct response ~les is true. For example, 
a response of 'Bill is' to (Sd) seems to convey that John h not 
leaving for Stockhoha tomorrow. Thus viewing some YNQs as 
wh*qm,,qions req.ires a rather more coml~lex representation than 
simply adding a wh-question as a third disjunct. * In addition, 
defining different representations for various YNQ subtypes seems 
a le~s than satisfactory solution to tbe linfitations presented by 
current representations of YNQs. A more unified solution to the 
problems identified by Bolinger and Kiefer would clearly be 
desirable. Such a solution is suggested by current research on the 
role conversational implieature plays in accounting for indirect 
re.~pons~s to YN~.~)s. 
III CONVERSATIONAL I'MPLICATURE AND YNQS 
In a large cl:~s of in,!irect respon:~e.~ to YNQs, query and 
response each refi, r to an entity, attribute, state, activity, or event 
that can bo viewed as appearing on sorae eea~e; such references 
"In f~et, the third di~jon~t would have to be something like 
~ KQ-~leaving(Jol, n,~3oekholm,to~,~,~rrou,} A tea~ingfz.Sterkl~olm,tomorrow). 
aThe idea.~ outlined in the following section are discussed in more detail in 
(tlir,~rhberg, 1984). 
will be termed scalars and responses in such exchanges will be 
termed scalar responnes, s In such scalar exchanges, questioners 
can infer both a direct response and additional implicit information 
flora the unreqm'sted information provided by the respondent. In 
{0) for example, Q is entitled to infer the direct response no or I 
don "~ know 
(6) Q: Are mushrooms poisonous? 
R: Some are. 
and the additional information that It believes that there may be 
mushrooms that are not poisonous, ew, n though 3z(rnashroom(z) 
A poism~ous(x)) does not IogicMly i-,{v an)" of this information. 
Clearly 'Some are' is an appropriate r,.~pouse to the query - more 
appropriate in fact than a simple no, wllich might convey that. no 
mushrooms are poisonous - but what makes it appropriate? 
Grire's (Grice, 1975) Cooperative Principle claims that, without 
contrary evide~cp, participants in convers~.tion assume their 
partners are trying to be cooperative. In consequence, they 
recognize certain conversational maxims, such as Grice's Mnzirn. 
of Quantit|l 
u I Make your eoutribution as informative as is 
required (for the current purposes of the exchange). 
b) Do not make your contribution more informative 
than is required. 
and his ~,~azint ol QuoJity 
Try to make your contribution one that is true. 
a) Do not say what you believe to be false. 
b) Do not. say that for which you I~k adequate 
evidence. 
Speaker and hearer's mutual recognition of these maxims may give 
rise to eort~erscttional ~mp~ieaturen: An utterance 
eonveraatios~allll intp~icates a proposition P when it conveys 
P by virtue of the bearer's assumption of the speaker's 
cooperativeness. While s speaker may not always obey the~e 
maxims, the hearer's expectations are based on her belief that such 
conventions represent the norm. 
A. Scalar Pred|eatlon 
Following Grice, Horn {flora, 1972) observed that, when a 
speaker refers to a value on some scale defined by eentantl," 
entai|ment 4, that value represents the highest value on its scale 
the speaker can t ruthful!y affirm. The speaker is saying as much 
{Quantity) as she truthfully (Quality) can. Higher values on that 
scale are thus implicitly marked by the speaker as not known to 
be the case or known not to be the ease. 5 Values lower on the 
scale will of course be marked as true, since they are entailed. 
Horn called this phenomenon scalar predleation, and 
Gazdar {Gazdar, 1979) later used a variation as the basis for a 
phenomenon he termed sea/at quantity irrtp\[ieature. Here a 
much revi~d and extended version will be termed scalar 
implleature. 
Horn's simple notion of scalar predication does provide a 
principled ba.~is for interpreting ({3) attd similar indirect responses 
to YNQs where scales are defined by entailment. Some is the 
highest value on a quantifier scale that R can truthfully affirm. 
Truth°values of higher scalars such as all are either unknown to R 
or believed by him to be false. Thus, if Q recognizes R's 
implieature, roughly, 'As far as 1 know, not all mushrooms are 
poisonous', she will derive the direct response to her query as no or 
I don ~ know. H must believe either that some mushrooms are not 
poisonous or that some mushrooms may not be poisonous. 
4W semantieMly entails Tiff T is true whenever W is. 
5Whether x speaker implicates ignorance or falsity of • value is t subject of 
~ome disagreement •merit Ilorn and those (Gasdar, lg7g, So~mes, 1082) who 
h•ve taken up his basic notion, In (ltirschberg, 1984) I contend that such 
implieatures should be viewed as didunctions, K(~T) V ~K(T), which may be 
dbamhiguated by the nature of the ordering relation or by the context. 
49 
d¢ 
It is also important to note that, in (6), were R simply to deny 
Q's query or to assert ignora~ce with a simple \[ don't know, Q 
would be entitled, by virtue of the Cooperative Principle, to 
assume that there is no scalar value whose truth R can in fact 
affirm. That is, Q can assume that, as far as R knows, there are 
no mushrooms that are poisonous, for otherwise R could commit 
himself to the proposition that 'some mushrooms are poisonous'. 
More generally then, 1-~ is obliged by the Cooperative Principle, 
and more especially by Joshi's (Josh}, 1982) modification of Grice's 
Maxim el Qua/itl/: 'Do not say anything which may imply for 
the hearer something which you the speaker believe to be false.', to 
provide an indirect response in (6), lest a simple direct response 
entitle Q to conclude some ,fa/,e iwtplieaturee. Thus indirect 
responses must be included among the set of all appropriate 
responses to a given YNQ, since in some cases they may be the 
most appropriate response R can make. 
B. Scalar Impllcature 
While scalar predication provides a principled explanation for {6), 
a revised and extended notion of aea/ar irrtplieature can 
account for a much larger class of indirect responses to YNQs. It 
can also suggest a revised representation of YNQs in general based 
upon this enlarged class of appropriate responses. 
Order}ors not defined by entailment and order}rigs other than 
linear orderings, including but not limited to set/set-member, 
whole/part, process stages, spatial relationship, prerequisite 
orderings, entity/attribute, lea hierarchy, or temporal ordering, 
permit the conveyance of scalar implicatures in much the same 
way that the entailed quantifer scale does in (6)~ In (7) the set/ 
member 
(7) Q: Did you invite the Reagans! 
R: I invited Nancy. 
(8~ Q: }lave you finished the manuscript? 
It: I've started a rough draft. 
relati,,nship orders the Rcagans and Nancy; R implicates that he 
has not invited Ronald, for instance. In 18), starting a rough 
draft precedes finishing a manuecript in the process of preparing 
a paper. So Q is entitled to conclude that R has not finished the 
manuscript or completed any later stage in this process, such as 
finishing the rough draft. 
More formally, any set of referents {bl,...,bn} that can be 
partially ordered by a relation O s can support scalar 
implicature. Any scale S that permits scalar implicature can be 
represented as a partiallg-ordered eet. For any referents bt, b z 
on S, b 2 is higher on S than b I iff blOb2; similarly, b I is lower 
on S than b~ iff blOb ~. Any pair b 1, b~ of ineontparable 
elements (elements not ordered with respect to one another by 
O) will be termed alternate values with respect to S. This 
redefinition of scale accommodates order}ors such as those 
mentioned above, while excluding orderings such as cycles, that do 
not permit scalar implieatute. It also helps define the inferences 
licensed when \[t affirms a higher or an alternate value, or when he 
denies or asserts ignorance of lower, higher, or alternate valses. 
For example, R affirms a higher scalar value than the value 
queried in Bolinger's example reproduced in (2). If difficult and 
impo.~Mble are viewed on a scale defined in d,.grees of feasibility, 
then Q can conclude that by affirming ghc higher value H has 
affirmed the lower. Similarly, R may affirm an alternate value, as 
he d~s in (3h}. If II sees Honoluh| and Hilo as b~,th members of a 
set of Hawaiian cities, he can affirm an unqueried set member 
(ltilo) to deny a queried member {llawaii). The affirmati,~n of an 
unqueried ah,'rnate value generally conveys the falsity or R's 
ignorance of the queried value. 
SA partial ord~-rin 9 may be defined as an irreflexive, tsymmr-trie, and 
transitive rel~.tiou. 
Speakers may also license scalar implicat,ires by denying scalars. 
The dual to Horn's notion of affirming the highest affirmable v:due 
would be negating the lowest deniable scalar. In such a denial a 
speaker may implicate his affirmation or ignorance of lower 
scalars. So, in exchanges like {9a), a value higher than a queried 
value {here, 
(9} Q: Did you write a check for the rent? 
a. R: l haven't mailed it yet. 
b. R: I haven't signed it. 
c. R: I didn't pay cash. 
a stage in the process of mortgage payment) may be denied to 
convey the truth of the queried value. R may also deny lower 
values (gb) or alternate vahscs (9c}. 
So, indirect scalar responses may be defined UlU,n a number of 
metrics and may involve the affirmation or negation of higher, 
lower, or alternate values. They may also involve the affirmation 
or denial of more than one scalar h~r a single query, as shown in 
(10). Ash';nine that Mary and Joe are brother and s:ster and both 
are known to Q and tL Also, Mary and Tim are fellow-workers 
with Q and R. Then to Q's question in {10), R may felicitously 
respond with any or the 
(10) Q: Does Mary like skiing? 
a. R: She loves iee-gkating. 
b. R: ,Joe loves cross-country. 
e. R: Tim likes cros~country. 
answers given - as well a~s a variety of others, such as 'Site n~ed 
to' or even 'Joe used to love ice-skating.' That is, R may base his 
response upon any one or more scalars he perceives as invoked by 
Q's query. In addition, a single lexical it(:m (here Mary} may 
invoke more than one scale: R may view Mary as a member of a 
family or of a set of fellow-workers, for example, to generate 
responses (10b) and (ll}c), respectively. 
C. A Scalar Representation of YNQs. 
Given this characterization of appropriate indirect responses, it is 
possible to model the exchanges present,,d above in the following 
way: 
1. For some query uttered by Q, let P V "P represent 
the query's desideratum; 
2. Let Pxl/bl,x2/b2,...,Xn/bnV-Pxl/b~,xg/b2,...,Xn/bn re- 
present the open propozition formed by substituting 
variables x I for each b i ir~vokcd by P that R perceives 
as lying on some scMe Si; 
3. Then P V'P • J~X,~z/xa,...,~n/Xn ~/%,%/~.,,...,.~Jx,, 
defines the set ~.,f possible responses to Q's query, where 
each a I repre.-.ents some scalar coo*currier with its 
corresponding b i on S i. 
4. A subset of these p~,ssit.qe re~ponses, the set of possible 
true respcmses, will be det~.rmined by 1¢ from his 
knowledge ba0:c, and an actual r~'sponsc ~l~lectcd. 7 
In 16), for example, the de.-.ider:dum {P V "q>) of Q's query is the 
generic '(all) mushrooms are poisonous' V 'not (all) mushrooms are 
poisonous', tiers R might perceive a single scalar all lying on a 
quantifier scale, ,onc//~¢ome/all. So, 'x I mushrooms are poisonous' 
V 'not x I \[all,brooms ace poisonous' represents the (,pen 
proF-sition formed b) substituting a variable for all in P, where x! 
ranges over the values on SI. nor~,/oorn,~/u!l. Then the set of 
p..-.ible resp(.n~:.~ tt, t~'s query, given P~'s choice of seal:~r, is 
dt,fin~.d by the affirmatiml or ~wgati~m of cach of the possible 
instantiations of 'al/x I mushrooms at, ~ poisonous', or the set {no 
nlushrool/is are poisoIIOUS.SO.~le L'lushfooIIlS are poisonous.all 
mushrooms are poisonous,-nno mushrooms are poisonons, -some 
7S~.e lliir~ehberg, l~t~41 rr.r farth~ r diseusslon of this self'ca}on process. 
50 
mushr-on~s :~r~ poisonous, ~ail r:,,a,hro,~ms are poisonous}. The 
set of po,.-ibh, true r,.sponscs will be a subset of this set, 
determined b)' It from Iris knowh:dgc ba.se. Note that a I and b l 
may in fact be identical. Thus, the simple direct responses, 
equivalent to 'All mushrooms are poisonous' and 'Not all 
mushrooms are poi.~t)nous', are accorumodated in this schema. 
Thi~ charact~,riz:ttion of potcnt.ial response.-, suggests a new 
repre~entath)n for YNt~s. l'oih)wing Hintikka, one might 
paraphrase the query in (6) as 'Bring it about that I know that x t 
mushro~Jnls are poisonous r~r that I know that. not x t mushrooms 
art.' poisonous t, where x I range~ over the values on some scale S t 
up.n which the qlo'ried v:due .~om( appears (assuming a many- 
sorted epi~temic logic). Thus the query alight be represented as 
! 3~l.~X I (so:;,e,xtENtA {KQ(X I mushrooms are 
pois,,nou~) V KQ~(X t mi, shrooms are poisonous)}}. 
For a query like that in (It)), an appropriate representation might 
be: 
! :3Sl-~Xt3S2.:\]x2~\]Sa3x.~ {Mary,xtESiAIove,x2ES 2 
Askiing.xaES3A {KQ{X 1 x 2 x3) V KQ~(X l x 2 x3)}}. 
lI may then instantiate each variable with any value from its 
domain in his response. 
In the gem'ral e~e, then, YNQs might be represented as 
3SI,...,:JSa3xI,...,3x~, {bI,x1ES 1 A .... A bn,XnCS a A 
{KQ(l'x I ...... n) V Kq'{Pxt ...... n )}" 
This representation shares some features of standard 
representations of wh-qm.stions, .~uggesting that it simply extends 
Kiefer's view of foct:s~ed "fNQs to all YNQs. However, there are 
several :dgnificant di~tincthms between this representation and 
standard repres,.ntatioas of wh-questk)ns, and, thus, between it and 
Kiefer's suggesthm. First, it restricts the domains of variables to 
scales invoked by corresponding scalars in the original queries 
desideratum and it includes a negative disjuuet. 'Do you like 
Ilonolulu?' for example might have as its desideratum 
::IS |-:Ix t :~S2::lx2"\]Ss3xa {you,xl ES IAlike,x=ES2 
Allonolulu,x.~ES s A {KQ(X t x~ xsJVKq~(X i x 2 xs)}}, 
while the corresponding wh-question 'What do you like?' would 
have as its desideratum 32 lfQfVou like z). Second, the 
representation prop,sed here allows for reference in a query to 
muhiple scalars, or, multiple focii, which Kiefer does not consider. 
Third, it awJids both the division of YNQs into focussed and non- 
focussed queries and the dependency between wh-responses and 
negative responses noted above; hence, the representation is 
simpler and more unified. So, YNQs are not represented as wh- 
questions, although Kiefer's focussed YNQs can be accommodated 
in this more general representation, which 1 will term a ~eel~," 
repreae~tatlo~. 
IV DISCUSSION 
A scalar representation of YNQs can accommodate a wide range 
of direct and indirect responses which are common in natural 
discourse but which current representations of YNQs cannot 
support. Of course, such a redefinition is no panacea for the 
limitations of current representations: In its current form, for 
instance, there are sonic appropriate responses to indirect speech 
acts, such as (ill, which it 
(11) Q: Can you tell me the time? 
R: It's 5:30. 
will not support. In other exchanges, such as {12), the notion of 
seale may seem less tha,~ natural, where a scale like attribute* of a 
(12) Q: Is she pretty? 
R: She's married. 
potcnHal date.: {pr~:ttg, unmarried,...} must be postulated to 
accommodate this query in the the representation proposed here. 
Too, tbe actual representation of a particular query may vary 
according to participants' differing perception of scalars invoked 
by it, as shown in (I0). Because scales are not defined in absolute 
terms, it is difficult to determine even an abstract specification of 
the set of all possible responses to a given query; should temporal 
and modal variables always be understood as implicitly evoked by 
any query, for example, as in {13)? However, if broad categories of 
sucb 
(13) Q: Is Gloria a blonde? 
a. R: She used to be. 
b. R: She could be. 
'understood' scales can be identified, much of this difficulty might. 
be alleviated. The representation proposed here does 
accommodate a far larger class of appropriate responses than 
representations previously suggested, and accommodates them in a 
unified way. With further refinement it promises to provide a 
useful tool for theoretical and computational treatments of YNQs. 
ACKNOWLEDGEMENTS 
1 would like to thank Aravind Joshi, Kathy McCoy, Martha 
Pollack, Sitaram Lanka, and Bonnie Webber for their comments on 
this paper. 
REFERENCES 
Bolinger, D. Yes-No Questions Are Not Alternative Questions. In 
Hiz, H. ( ,Ed.}, Qucstiona. Dordrecht (Neth): Reidel, 1978. 
Gazdar, G. A Solution to the Projection Problem. In Oh, C.-K. 
and Dinneen, D. (Eds.), Syntax and Semantics. New York: 
Academic Press, 1979. 
Grice, H. P. Logic and Conversation. In Cole, P. and Morgan, J.L. 
(F_Ms.}, Syntaz and Semantic*. New York: Academic Press, 
1975. 
Hintikka, J. Answers to Questions. In Hiz, H. tEd.), Question~. 
Dordrecht (Neth.): Reidel, 1978. 
Hirschberg, J. Scalar lmplicature and Indirect Responses to Yes- 
No Que*tiona (Teeh. Rep. MS-CIS-84-9). University of 
Pennsylvania, April 198t. 
Hobbs, J. and Robinson, J. Why Ask? Di*cour, e Procesaes, 1979, 
Vol. ~. 
Horn, L. R. On the Semantic Properties of Logical Operators in 
English. Doctoral dis~rtation, University of California at 
Los Angeles, 197 ° . 
Joshi, A.K. Tile Role of Mutual Beliefs in Question-Answer 
Systems. In Smith, N. {Ed.}, Mutual Belief. New York: 
Academic Press, 1982. 
Kiefer, F. Yes-No Questions as WH-Questions. In Searle, J., Kiefer, 
F., and Bierwisch, J. (Eds.), Speech Act Theory and 
Pragmatics. Dordrecht (Neth): Reidel, 1980. 
Pollack, M. E., Hirschberg, J., and Webber, B. Uaer Participation 
in the Rca*oning Proeessea of Ezpert Systems (Tech. Rep. 
MS-CIS-82-9). University of Pennsylvania, July 1982. A 
shorter version appears in the AAAI Proceedings, 1982. 
Soames, C. How Presuppositions Are Inherited: A solution to the 
projection problem. Lingui*tie lnquir~l, 1982, 13~3), 483-545. 
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