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<?xml version="1.0" standalone="yes"?> <Paper uid="C94-1039"> <Title>Adjuncts and the Processing of Lexical Rules</Title> <Section position="2" start_page="0" end_page="0" type="metho"> <SectionTitle> BCN RUG Groningen </SectionTitle> <Paragraph position="0"> {vannoord, goss e} 0let. rug. n\].</Paragraph> </Section> <Section position="3" start_page="0" end_page="0" type="metho"> <SectionTitle> Abstract </SectionTitle> <Paragraph position="0"> The standard HPSG analysis of Germanic verb clusters can not explain the observed narrow-scope readings of adjuncts in such verb clusters. null We present an extension of the HPSG analysis that accounts for the systematic ambiguity of the scope of adjuncts in verb cluster constructions, by treating adjuncts as members of the sul)eat list. The extension uses power-Nl reeursive lexical rules, implemented as complex constraints. We show how 'delayed evaluation' teehMques from constrMnt-loglc programming can be used to process such lexical rules.</Paragraph> </Section> <Section position="4" start_page="0" end_page="0" type="metho"> <SectionTitle> 1 Problem Description </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 1.1 Dutch Verb Clusters </SectionTitle> <Paragraph position="0"> Consider the following Dutch subordinate sentences. null (1) dat Arie wil slapen that Arie wants to-sleep (2) dat Arie Bob wil slaan that Arie Bob wants to-hit that Arie wants to hit l/ot) (3) * (lat Arie Bob wil slapen that Arie Bob wants to-sleep that Arie wants to sleep lloh (4) * dat Arie wil Bob slaan (5) dat Arie Bob cadeautjes wil geven that Arie Bob presents want to-give that Arie wants to give presents to Bob (6) * dat Arie Bob wil cadeautjes geven dat Arie wil Bob ca(leautjes geven (7) dat Arie Bob zou moeten kunnen willen knssen that Arie Bob should must can want to-kiss that Arie should be able to want to kiss Ilob The examples 1-3 indicate that in l)utch the arguments of a main verb can be realized to the left of an intervening auxiliary verb, such as a modM verl). Furthermore the sentences in d-6 indicate that in such constructions the arguments must 1)e realized to the left of the auxiliary verbs. In 7 it is illustrated that there can he any numl)er of auxiliaries.</Paragraph> </Section> </Section> <Section position="5" start_page="0" end_page="257" type="metho"> <SectionTitle> 1.2 The IIPSG analysis of verb- clusters </SectionTitle> <Paragraph position="0"> The now standard analysis within t\[PSG of such verb-clusters is based oil ideas from Categorial Grammar (cf. for example Moortgat (1988)) and defined within the HPSG flamework by IIinrichs and Nakazawa (1989). In this analysis auxiliary verbs subcategorize for an unsaturated verb-phrase and for the compleinents that are not yet realized by this verbl)hrase. In other words, the arguments of the embedded verl)-phrase are inherited by the auxiliary.</Paragraph> <Paragraph position="1"> For example, the auxiliary 'wil' might be defined as in Iigure 1. If we assume an ai)plication rule that produces flat vp-structures, then we obtain the derivation in figure 2 for tim in-</Paragraph> <Paragraph position="3"> case of adjuncts. For example, the following Dutch subordinate sentences are all systematically ambiguous between a wide-scope reading (adjunct modilies tile event introduced by the auxiliary) or a narrow-scope reading (adjunct modi%s the event introduced by the main verb).</Paragraph> <Paragraph position="4"> (9) dat Arie vandaag Bob wil slaan that Arie today Bob want to-hit that Arie wants to hit IIob today (10) dat Arie hot artikel op tljd probeerde, op te stllren that Arie the article on time tried to send that Arie tried to send the article in time (11) dat Arie Bob de vronwen met een verrekljker zag bekljken that Arie Bob the women with the telescope saw look-at that Arie saw Bob looking at the women with the telescope Firstly note that tile treatment of adjuncts as presented in Pollard and Sag (in press), cannot be maintained a.s it simply fails to derive any of these sentences because the introduction of adjuncts is only possible as sisters of saturated elements. The fact that ~trguments and adjuncts can come interspersed (at least in languages such as Dutch and German) is not accounted for.</Paragraph> <Paragraph position="5"> A straight forw~ml solution to this problem is presented in Kasper (in prepar~tion). Here adjmwts and arguments are all sisters to a head. Tim arguments should satisfy the subcat requirements of this hea.d - the adjuncts modify the semantics of the head (via a recnrsively defined a.djuncts principle).</Paragraph> <Paragraph position="6"> The main I)rol)lem for this treatment of ad.iuncts is that it cannot explain the narrow-scope readings observed above, if adjuncts modify the. head of the phrase they are part of then we will only obtain the wide-scope rea,dings. null If we assume, on the other hand, that ad.jnncts are oil the subcat list;, then we will obtain both readings straightforwardly. In tile narrow-scope case tile adjunct is on the snbcat list of the embedded w~rb, and then inherited by the matrix w.~rb. In the wide-scope case tilt adjunct simply is on the subcat list of the matrix verb. in the next section we present a treatment of adjuncts in which each adjunct is subcategorized for. By me,ms of lexical rules we are able to obtain the. effect that there can be any mmfl)er of adjuncts. We also sketch how the semantics of modification might be delined.</Paragraph> </Section> <Section position="6" start_page="257" end_page="257" type="metho"> <SectionTitle> 2 Adjuncts as Arguments </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="257" end_page="257" type="sub_section"> <SectionTitle> 2.1 Adding adjuncts </SectionTitle> <Paragraph position="0"> The previous section presented an argument that VP modifiers are selected for by the verb.</Paragraph> <Paragraph position="1"> Note that this is in line with earlier analyses of adjuncts in HPSG (Pollard and Sag, 1987) which where abandoned as it was unclear how the semantic contribution of adjuncts could be defined.</Paragraph> <Paragraph position="2"> IIere we propose a solution in which adjuncts are members of the subcat list, just like ordinary arguments. The difference between arguments and adjuncts is that adjuncts are 'added' to a subcat list by a lexical rule that operates recursively. 1 Such a lexical rule might for example be stated as in figure 3.</Paragraph> <Paragraph position="3"> Note that in this rule the construction of the semantics of a modified verb-phrase is still taken care of by a rood feature on the adjunct, containing a val and arg attribute. The arg attribute is unified with the 'incoming' semantics of the verb-phrase without the adjunct. The val attribute is the resulting semantics of the verb-phrase including the adjunct. This allows the following treatment of the semantics of modification 2, cf. figure 4.</Paragraph> <Paragraph position="4"> We are now in a position to explain the observed ambiguity of adjuncts in verb-cluster constructions. Cf.: (12) dat Arie Bob vandaag wil kussen that Arie Bob today wants to-kiss In the narrow-scope reading tim adjunct is first added to the subeat list of 'kussen' and then passed ou to the subcat list of the auxiliary verb. In the wide-scope reading the adjunct is added to the subcat list of the auxiliary wM~.</Paragraph> <Paragraph position="5"> The final instantiations of the auxiliary 'wil' for both readings are given iu figure 5.</Paragraph> </Section> <Section position="2" start_page="257" end_page="257" type="sub_section"> <SectionTitle> 2.2 Discussion </SectionTitle> <Paragraph position="0"> A further problem concerning the syntax of adjuncts is posed by the fact that adjuncts can take part in unbounded dependency construelions. Lexical treatments of the kind presented in Pollard and Sag (in press), chapter 9 assume that a lexlcal rule is responsible for 'moving' lcf. Miller (1992) for a similar suggestions concern- null an element from the subcat list to the slash list. Such an account predicts that adjuncts cau not take part in such unbounded dependency constructions. In Pollard and Sag (in press), chapter 9 a special rule is introduced to account for those cases where adjuncts do take part in UI)Cs. '\['he treatment that we propose for adjuncts obviates the need for such an 'ad-hoc' rule.</Paragraph> <Paragraph position="1"> Clearly many details concerning the syntax of adjuncts are left untouched here, such as the quite subtle restrictions in word-order possibilities of certain adjuncts with respect to arguments and with respect to other adjimcts. In the current framework linguistic insights concerning these issues could be expressed as constraints on the resulting subcategorization list (e.g. by means of LP-constraints).</Paragraph> <Paragraph position="2"> lit should also be stressed that treating adjuncts and arguments on a par on the level of subcategorization does not imply that observe<\[ differences in the behavi<)r of adjuncts and arguments could not be handled in the proposed framework. For example the difference of adjuncts and arguments in the case of left dislocation in Dutch (exemplified in 13-16) can be treated by a lexica\] rule that oper~tes on the subcat list before adjuncts are added.</Paragraph> <Paragraph position="3"> (13) De voorstelling duurt een uur Tim show takes an hour (l,l) l';en uur, dat duurt de voorstelling (15) Arieen Bob wandelen een uur Arie and Bol) wall< an hour (16) * l&quot;en uur, dat wandelen Arieen Bob 3 Processing Lexical Rules</Paragraph> </Section> <Section position="3" start_page="257" end_page="257" type="sub_section"> <SectionTitle> 3.1 Lexical Rules as Constraints on Lexical Categories </SectionTitle> <Paragraph position="0"> Rather than formalizing the 'add-adjuncts' rule as a lexical rule we propose to use recursive constraints on lexical categories. Such lexical constraints are then processed using delayed ewduation techniques, a Such an approach is more promising than an off-line approach that precomputes the effect aRefer to Carpenter (1991) for a proof of TurilLg equivalence of simple eategorial grammar with recurslve lexical rules.</Paragraph> <Paragraph position="2"/> <Paragraph position="4"> and time adverbials) will generally be encoded as presented, where R0 is a meta-wu'iable that is instantiated by the restriction introduced by the adjunct. Operator ~ulverblals (such as causatives) on the other hand introduce their own quantified state of aft'airs. Such mlverbials generally are encoded as in the following examph', of the adverbial 'toewdlig' (accidentally). Adw.,rbials of the first type add a restriction to the semantics of the verb; ;Ldwn'bials of the second type introduce a new scope of modification.</Paragraph> <Paragraph position="5"> of lexical rules by compil~tion of the lexicon, as it is unclear how recursive lexical rules can be treated in such an architecture (especially since sOllle recursive rules e:ut easily lead to an infinite number of lexical entries, e.g. tlle adjuncts rule).</Paragraph> <Paragraph position="6"> Another alternative is to consider lexical rules as 'ordinary' unary rules. If this technique, is applied for the lexical rules we have envisaged here, then (unary) derivations with unbounded length have to be <:mlsidet'ed.</Paragraph> <Paragraph position="7"> \]f we formalize lexieal rules as (oomph,x) constraints on lexical categories then we are able to use delayed evaluation techniques for such constraints.</Paragraph> <Paragraph position="8"> Assume that the 'underlying' feature structure of a verb is given by a definition of 'stem' (e.g. as the example of 'wil' abow'., or as the example of a simple transitive verb such as 'kussen' (to-kiss) in figure 6).</Paragraph> <Paragraph position="9"> Such a feature-structure is not the actual category of the verb -- rather this category is define.d with complex eonstraints with re.</Paragraph> <Paragraph position="10"> speet to this base form. \]lere the constraint that adds adjuncts to the subc:tt list has our</Paragraph> <Paragraph position="12"> l;'igure (i: (h~.tet,;ory for 'kussen' (to Idss) special attention, but there, is also a constraint tha.t adds a snbj<'.ct to the subeat list (as part of the in\[lection constraint for finite verbs) and a constraint that pushes an element from the subeat list to slash (to trea,t utll)ounded dependencies along the lines of eha.pter 9 of Pollard and Sag (in press)), etc. Thus a \]exical entry might be defilmd as in ligure 7.</Paragraph> <Paragraph position="13"> \],exical rules are regarded as (complex) constrah~ts ill l;his framework because it allows an imple.mentation using delayed evaluation techniques from logic progrannning. The idea is</Paragraph> <Paragraph position="15"> lea : vandaag , lea: : bob , lez : arie dir : left E dir : left tl dir: left the sentence ~Arie Bob vandaag wil kussen'. In tit(', narrow-scope rending the adverbial occurs both on the subeat list of the embedded verb and on the subeat list of the matrix verb -- indicating that the embedded verb introduced the adjunct. In the wide-scope reading the adverb only occurs on the subcat list of the matrix verb.</Paragraph> <Paragraph position="17"> spect to a base form using complex constraints.</Paragraph> <Paragraph position="18"> Subject addition is a constraint associated with finite inflection.</Paragraph> <Paragraph position="19"> that a certain constraint is only (partially) evaluated if 'enough' information is available to do so successfully. As a relatively simple example we consider the constraint that is responsible for adding a sul)ject as the last element on a subcat list of finite verbs. As a lexical rule we might define: \[FINITE 1 subj: Subj ==> \[ sc : St. (Subj) \]</Paragraph> <Paragraph position="21"> If we use constraints the definition can be given as in figure 7, as part of the constraint associated with finite morphology. Note that the two approaches are not equivalent. If we use lexical rules then we have to make sure that the addsubject rule should be applied only once, and only for finite verbs. As a constraint we simply call the constraint once at the appropriate position.</Paragraph> <Paragraph position="22"> The concatenation constraint (associated with the ~dot' notation) is defined as usual: concat (0 , A, a).</Paragraph> <Paragraph position="23"> eoneat((BIC), A, (II\]D)) : concat(C, A, l)).</Paragraph> <Paragraph position="24"> If this constraint api)lies on a category of which the subcat list is not yet fully specified (for example because we do not yet know how many adjuncts have been added to this list) then we cannot yet compute the resulting subcat list.</Paragraph> <Paragraph position="25"> The constrMnt can be suimessfully applied if either one of the subcat lists is instmttiated: then we obtain a finite miml)er of i)osslble sohltions to the. colistraint.</Paragraph> <Paragraph position="26"> The relation add_adj recursively descends through a subcategorization list and at each position either adds or does not add an adjunct (of the appropriate type). Its definition is given in figure 8. Note that it is assumed in this definition that the scope of (operatortype) adverbials is given by the order in which they are put in in the subcategorization list, i.e. in the obliqueness order. 4 4Cf. Kasper (i,, preparation) for discussion of this point, also in rehttion with adjm, cts that introduce qmuttiflers. Note that in our approach dilR.'rent possibilities can be defined.</Paragraph> <Paragraph position="27"> I SIGN \] SIGN 1 add_adj( sc : A sc : J sere : B ' sere : K ) :subj : Subj subj : Subj add_adj(A, J, B, K).</Paragraph> <Paragraph position="28"> ~dd-~dj(0, 0, A, a).</Paragraph> <Paragraph position="29"> add_adj((CID), (ClE), A, n):add_adj(D, E, A, B).</Paragraph> <Paragraph position="30"> add_adj(A,( rood: arg : B w,l : l,; add_adj(A, D, I,;, C).</Paragraph> <Paragraph position="31"> ID), 1~, C):-</Paragraph> </Section> <Section position="4" start_page="257" end_page="257" type="sub_section"> <SectionTitle> 3.2 Delayed evaluation </SectionTitle> <Paragraph position="0"> For our current purposes, the co-routining facilities offered by Sicstns Prolog are powerful enough to implement a delayed evaluation strategy for the cases discussed al)ove. For each constraint we declare the conditions for evMuating a constraint of that type by means of a block declaration. For example the concat constraint is associated with a declaration: '- block coneat(-,?,-).</Paragraph> <Paragraph position="1"> This declaration says that evaluation of a c~dl to concat should be delayed if both the Iirst and third arguments are currently variable (uninstantiated, of type &quot;toP). It is clear fr<>m the definition of concat that if these arguments are instantiated then we can evahm.te the constraint in a top-down manner without risking non-termination, l!',.g, the goal concat((A, B), C, D) succeeds by insta.ntiating D as the list (A,I\]\]C).</Paragraph> <Paragraph position="2"> Note that block declarations apply recursively. If tit(: third argument to a call to coneat is instantiated as a list with a wu'iahle tail, then the evaluation of the recursive al)l)lication of that goat might be blocked; e.g. ewduation of the goat co,~.~(A, (S j), <nit>)s.e,'.oeds either with both A and C instantiated as the empty list and by unifying Sj ;rod B, or with A instantiated as the list (l\]\[l)) for which the constraint concat(D, (Sj), C)has to be satistied. Similarly, for each of the other constraints we declare the conditions under which the constra.int can be ewluated. For the add_adj constraint we define: &quot;- block add_adj(?, -, 7, 7).</Paragraph> <Paragraph position="3"> One may wonder whether in such a,n architecture enough information will ever become available to allow the evaluation of any of the constraints, hi general such a prol)lem may surface: the parser then finishe.s a derivation with a large collection of constraints that it is not ~dlowed to evaluate - and hence it is not clear whether the sentence associated with that derivation is in fad; gram m~tical (as there. may 1)e no solutions to these constraints).</Paragraph> <Paragraph position="4"> The strategy we have used successfitl/y sofar is to use the structure hypothesized by the parsm' as a 'generator' of information. For example, given that the parser hypothesizes the al)plication of rules, and hence of certain instmttiations of the sul)cat list of the (lexicM) head of such rules, this provides information on the subcat-list of lexical categories. Keep-ing in mind the definition of a lexical entry as in figure 7 we then are able to ewfluate each of the constraints O)l the wdue of the subcat list in tl,rn, starting with the push_slash constraint, up through the inflection and add_adj constraints. Thus ra.ther than using the consir.tints as q)uilders' of subcat-lists the constraints :~re evaluated by checking whether a subcat-list hypothesized by the parser can be related to a sat)cat-list provided by a verbstein, in other words, the \[1GW of information in the definition of Ie:~:ical_entry is not as the order of constraints might suggest (froln top to 1)ottom) but ratht, r the other way around (from hottom to top).</Paragraph> </Section> </Section> class="xml-element"></Paper>