File Information
File: 05-lr/acl_arc_1_sum/cleansed_text/xml_by_section/metho/94/c94-2186_metho.xml
Size: 35,401 bytes
Last Modified: 2025-10-06 14:13:40
<?xml version="1.0" standalone="yes"?> <Paper uid="C94-2186"> <Title>EXPLOITING REFERENCE INTERACTION IN RESOLVING TEMPORAL REFERENCE</Title> <Section position="1" start_page="0" end_page="0" type="metho"> <SectionTitle> EXPLOITING REFERENCE INTERACTION IN RESOLVING TEMPORAL REFERENCE Kohji DOHSAKA NTT Basic Research Laboratories </SectionTitle> <Paragraph position="0"/> </Section> <Section position="2" start_page="0" end_page="0" type="metho"> <SectionTitle> ABSTRACT </SectionTitle> <Paragraph position="0"> q'his paper provides an account of the role that the interaction between nominal and temporal reference plays in resolving temporal reference. Exploiting this interaction in resolving temporal reference clarifies how the process of resolving nominal reference interacts with the process of resolving temporal reference, and how a restricted set of worht knowledge contributes to resolving temporal reference.</Paragraph> </Section> <Section position="3" start_page="0" end_page="1138" type="metho"> <SectionTitle> 1 INTRODUCTION </SectionTitle> <Paragraph position="0"> B.esolving reference or anaphora is of great interest in computational linguistics and formM semantics.</Paragraph> <Paragraph position="1"> Research on reference began with the development of models to account for nominal reference bronght about by the usage of nominal expressions such as definite noun phrases and pronominals (Grosz, Joshi and Weinstein 1983; Kameyama 1986). Recently a number of researchers have indicated that temporal expressions such as tense morphemes and temporal adverbials can be regarded as referring expressions and have proposed models for temporal reference resolution (Hinrichs 1986; Hwang and Schubert 1992; Kameyama, Passonnean and Poesio 1993; Lascarides 1.992; Partee 1984; Song and Cohen 1991; Webber 1988).</Paragraph> <Paragraph position="2"> Sentences in a dialogue describe eventualities 1 and introduce them into the context. The time of an eventuality described by a sentence is interpreted as temporally related to the times of other eventualities that were introduced into the context earlier in the dialogue. Temporal expressions are regarded as referring expressions since they convey information about the time of an eventuality, which is interpreted relative to the times of other eventualities in the context. Resolving temporal reference means determining what temporal relationships exist between an eventuality described by a sentence of a dialogue and eventualities that have been introduced into the context earlier in the dialogue. 2 Resolving temporal reference is requisite to many tasks, such as designing a natural language interface to a planning system in which temporal information is crucial (Crouch and Pullman tan event.uality is the general term for an event, process or state, due to Bach (1986).</Paragraph> <Paragraph position="3"> ~The chief concern here is temporal reference to intersentential context. Thus this paper does not address the probiem of determining what temporal relationships an eventuality described by a clause of a sent, ence has with eventualities described by other clauses of the same sentence. This problem is covered by Brent (1990), Itwang et al. (1992), and Reichenbaeh (1947). 1993).</Paragraph> <Paragraph position="4"> To understand the notion of temporal reference, consider the following dialogue, (dl). a Assume tha~ dialogue participants, Bill and John, mutually know that John received an e-mail message from Mary.</Paragraph> <Paragraph position="5"> Dialogue (dl) (sl) Bill: Mary karano mail wa mot-teirn-yone? from mail ToP have~PRESENT You have the mail from Mary, don't your (s2) John: Keshi-ta-kedo.</Paragraph> <Paragraph position="6"> (s4) John: Sochira niwa tensoushi-ta-hazuda-yo.</Paragraph> <Paragraph position="7"> you DAT forward~PhsT-sure.</Paragraph> <Paragraph position="8"> I'm sure that l forwarded it to you.</Paragraph> <Paragraph position="9"> (s5) John: Sochira no mail box ni at-ta-desho? you GFN mail boz&quot; in be-PAST.</Paragraph> <Paragraph position="10"> II was in your mail bo~', wasn't it?.</Paragraph> <Paragraph position="11"> Sentence (s2) describes an eventnality of deleting, Ed, and sentence (s4) describes an eventuality of forwarding, F/. Both eventualities are past ones, since the matrix verbs, &quot;tensousnru (forward)&quot; and &quot;kesu (delete)&quot;, 4 describe momentary acts and are accompanied with the past-tense morpheme &quot;ta&quot;. Although the tense morphemes of sentences convey information about the times of eventualities described by the sentences, the context also imposes restrictions on the times of the eventualities. In dialogue (dl), the time of tQ described by (s4) is interpreted as relative to the time of \]'d~ in the context: i.e. the time of E/ is before the time of 1,2d. in this sense, the time of 1~ is referred to in uttering sentence (s4).</Paragraph> <Paragraph position="12"> Existing models of temporal reference account for the parMlel between temporal and nominal reference.</Paragraph> <Paragraph position="13"> Itowever, as I will state in see. 2, existing models fail to explain the interaction between temporal reference and nominal reference (reference interaction for short), i{eference interaction is a phenomenon in which tile process of resolving nominal reference inahl extfibiting a .Japanese dialogue, English words such as &quot;Mary&quot; mtd &quot;mail&quot; are used only for easy comprehensibility, hi addlt, ion, sentence-final forms such as &quot;yone&quot;, &quot;kedo&quot;, &quot;yo&quot;, and &quot;desho&quot; indicate mental states of file speaker that are/mrelated to the subject of this paper.</Paragraph> <Paragraph position="14"> 4 &quot;tensoushi-&quot; and &quot;keshi-&quot; in file dialogue are inflections of the verbs &quot;tensousm'u&quot; and &quot;kesu&quot; respectively. teracts with the process of resolving temporal reference, when an utterance involves temporal and nominal reference at the same time. l)ue to as1 insutticient account of the reference interaction, existing models cannot show how the process of resolving nominal reference Mfects the process of resolving temporal reference. null The chief concern of this paper is to describe the role that the reference interaction plays in resolving telnporal reference and demonstrate that the reference interaction serves to clarity how a restricted set of world knowledge contributes to the resolution process. I focus on sentences with past-tense morphemes in Japanese dialogues. Previous work also used past-tense sentences as a touchstone to show the validity of a model (IIinrichs 1986; Kameyama ct al. 1993; Lascarides 1992; Partee 1984; Webber 1988). As I will state in sec. 2.2, the retk'xence interaction is not a domestic plleuolnenon in Japanese dialogues.</Paragraph> <Paragraph position="15"> In sec. 2, I argue that existing models do not de-.</Paragraph> <Paragraph position="16"> count for the reference interaction, that the reference interaction plays an important role in an account of how temporal reference is resolved, and that exploiting the reference interaction clarifies how a rest, rioted set of world knowledge serves to resolve tempered reference. In sec. 3, a tYamework is presented, within which the reference interaction is exploited in resolving temporal reference. In sec. 4, 1 demonstrate how f, he framework works. In sec. 5, \[ smnmarize the claims of this paper and describe fnture, work.</Paragraph> </Section> <Section position="4" start_page="1138" end_page="1139" type="metho"> <SectionTitle> 2 PROBLEMS WITH EXISTING MODELS </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="1138" end_page="1139" type="sub_section"> <SectionTitle> 2.1 Approaches in existing models </SectionTitle> <Paragraph position="0"> In existing models, when the t, ime, 7', of an eventalality described by a sentence of a dialogue is given, the problem of resolving temporal reference is divided into (i) that of identifying the time, 71/, of an eventuality that has been introduced into the context, and (ii) that of determining what temporal relationship hohls between 7' and 7):.</Paragraph> <Paragraph position="1"> The notion of temporal Ibcus is nsed to solve proh.lem (i). ','he notion was introduced by Webl,er (~988), Dialogue participants pay attention to the time of an eventuality that is in the temporal focus. '\['he time, 51', of an eventuality described by the cnrrent sentence is interpreted according to the time, Ttf, in the temporal focus. Existing models that apply to intersentential context use the notion of temporal focus (llwang el el, 1992; Song ct el. 19911. Kameyama et el. (1993) refined the. notion of temporal focus and proposed the notion of temporal centering. In formal semantics, models of temporal anaphora based on discourse representation theory have been proposed (ltinrichs 7198{3; Partee 1984). 'Fhese models concentrate on the tense interpretation of adjacent sentences its a narrative discourse. Thus, the time of ;m ew;ntuality described l)5' a sentence immediately preceding tile current sentence can be regarded as being in the temporal {hens.</Paragraph> <Paragraph position="2"> There ~r0. two ~tpproaches to prol)lcm (ii): (ii-a) av approach based on linguistic cuen such as tense morphelnes, the aspectual class of verbs, and the descriptive order of eventualities in a dialogne; (ii-b) an approach based oil worht knowledge of the causal relationships between eveutnalities.</Paragraph> <Paragraph position="3"> With regard Co approach (ii-a), the following default interpretation rules (ilinrichs 1986; Kameyama et el. 1993; bascarides 1992; Partce 1984; Webb0r 19881 have been used. '~ 'De.fault into.rpretation rules) Provided that an eventuality, tC/, is described by the current sentence, the time of an eventuality, let\], is in the temporal focus, and both/',' and \[C/t/ are past.</Paragraph> <Paragraph position="4"> eventualities, then (R1) The time of E is after the time of/C/tf if both IC/ and l';tf are non-st, drive, (1{2) The time of/C/ contains the time of ICe\] if \]C/ is stative and l','tf is non-stative.</Paragraph> <Paragraph position="5"> These rules are t;ermed default interpretation rules since they are utilized when world knowledge of causality is not available.</Paragraph> <Paragraph position="6"> \[n approach (ii-b), the temporal relationship between l,\] and .lC/tf is determined according to world knowledge of the causal relationships between eventualities. Lascarides (1.9!t2) presented a model based on a theory of defeasihle inference for integrating world knowledge of causality with the process of determining the temporal and causal relationships between even tualities mentioned in a discourse. This approach was also adopted in a model proposed by Kameyama ct el.</Paragraph> <Paragraph position="7"> (1993). In these models, approaches (ii-~) and (ii-b) are unified within a single framework. Let me call the interpretation based on approach (ii-a) the (lefanlt interpretation, and the interpretation based on approach (ii-b) the knowledge-based interpretation.</Paragraph> <Paragraph position="8"> The knowledge~based interpretation is preferred over the default interpretation when they disagree.</Paragraph> <Paragraph position="9"> l,et me explain how existing models work by using (tialogue (dl) ~ as, example. 1 focus on how (s4) i,, interpreted, assuming that the time of /~'a is in the. temporal focus, l)eNnlt interpretation rule (hi.l) says that the Lime of \]Q must be after the time of lea sittce both eventualities are not>stative, past eventualities. Ilowevcr, the relevant interpretation is that F,/ temporally precedes l','a. Thus, the default interpretation does not coincide with the relevant interpretation. In this case, existing models resort to world knowledge of the ransal relationships between PS'a and Ej. ltow.</Paragraph> <Paragraph position="10"> cw'.r, existing models do not clarify what kind of world knowledge is use.d (Kameyama et el. 1993; I,ascarides 1992). In this sense, the world knowledge used in existing models is unrestricted. 1 agree with such an approach its that various causal relationships are in-volved ill the process of resolving reference. IIoweveL it is desirable to find a restricted set of world knowledge and avoid resorting directly to the entire set of ~Note that the time of a stative even~uallty is usually nc)t regarded as being in the t.emporal focus.</Paragraph> <Paragraph position="11"> world knowledge of causality since such knowledge is enormous.</Paragraph> <Paragraph position="12"> Consequently, existing models exploit the notion of temporal focus or temporal center, which serves only to show that temporal reference is accounted for in the same way as nominal reference. However, existing models do not explain how the process of resolving nominal reference affects the process of resolving temporal reference and assume that the entire set of knowledge of causality can be used.</Paragraph> </Section> <Section position="2" start_page="1139" end_page="1139" type="sub_section"> <SectionTitle> 2.2 Reference interaction </SectionTitle> <Paragraph position="0"> In this section, I argue that the notion of reference interaction provides an account of the temporal reference in (s4), which existing approaches ignore. Moreover, a restricted set of world knowledge can be used to explain the reference interaction.</Paragraph> <Paragraph position="1"> Sentence (sl) introduces an individual 6, M, which is an e-mail message. Sentence (s4) involves nominal reference to M: tile object of &quot;tensousnrn (forward)&quot; is zero-pronominalized and refers to M. Moreover, sentence (s4) involves the interaction between nominal and temporal reference. That is to say, what the object being forwarded is affects what the time of forwarding is. I will explain this below.</Paragraph> <Paragraph position="2"> When someone forwards something to someone else, the time of forwarding must be during the time when the object being forwarded exists. In other words, the time of forwarding depends on what the object being forwarded is. Moreover, when someone deletes something, the time when the object being deleted exists must be before the time of deleting. This kind of world knowledge can be regarded as knowledge of temporal relationships between eventualities and the existential status of individuals. Judging fi:om such knowledge, the eventuality of forwarding, EI, cannot temporally follows the eventuality of deleting, Ea. This is because both the object of &quot;kesu (delete)&quot; and the object of &quot;tensousuru (forward)&quot;refer to M, so the time of t~'f must be during the time when M exists and the time when M exists rnust be before the time of Ed, The interpretation consistent with such knowledge is that /~Sf temporally precedes Ea. Consequently, identifying the referent of the zero-pronominalized object of/Q serves to resolve temporal reference, and the knowledge of temporal relationships between eventualities and the existential status of individuals can be used to explain the reference interaction. 7 Moreover, knowledge of the temporal relationships between eventualities and the existential status of individnals can be regarded as a restricted set of world knowledge of causality. It is restricted because given an eventuality, E, we have only to allow for the individuals that constitute E and do not have to allow degflere, &quot;individual&quot; is used as a term for a single person or thing.</Paragraph> <Paragraph position="3"> 7In this paper, only nominal reference to individuals is allowed for.</Paragraph> <Paragraph position="4"> for all eventualities that can be causally related to E. Exploiting the reference interaction clarifies how such a restricted set of world knowledge contributes to resolving temporal reference. When such restricted world knowledge is sufficient to resolve temporal reference, immediate recourse to the entire set of world knowledge of causality call be avoided. Note that such knowledge is not selected arbitrarily. It is the knowledge that is necessary for explaining the reference interaction. null Next I review two existing proposals that are related to the argument above. First, Hwang el al.</Paragraph> <Paragraph position="5"> (1992) argued that resolving temporal reference requires plausible inference that can interact with various processes such as resolution of anaphora, introduction of new individuals and identification of spatial and temporal frames. They also argue that the plausible inference has to rely on world knowledge such as that one normally would not buy broken things (IIwang eC/ al. 1992: p.239). Their argument agrees with the approach presented here. They did not, however, present a concrete model to support the argument.</Paragraph> <Paragraph position="6"> Second, Webber and Baldwin (1992) discussed the integration of two independent mechanisms for context-change by entity introduction and by event simulation. The idea of integrating these context-change mechanisms and that of exploiting the reference interaction in resolving reference share the view that the relationships between eventualities and the existential status of entities or individuals serve in interpreting referring expressions. They, however, focused on interpreting nominal reference made by the use of definite nouns, rather than on the problem of resolving temporal reference by exploiting the reference interaction, which is the chief concern of this paper.</Paragraph> <Paragraph position="7"> Finally, it is easy to see that the reference interaction also occurs in an English dialogue. In an English counterpart of (dl), the pronoun &quot;it&quot; is used the same way as a Japanese zero pronoun is used. l,ikewise, the restricted knowledge stated above is common to Japanese and English.</Paragraph> </Section> </Section> <Section position="5" start_page="1139" end_page="1141" type="metho"> <SectionTitle> 3 A FRAMEWORK </SectionTitle> <Paragraph position="0"> A framework is presented, within which the reference interaction is exploited in resolving temporal reference. First, in sec. 3.1, the descriptive device is shown. Next, in sec. 3.2, the process of resolving temporal reference is described.</Paragraph> <Section position="1" start_page="1139" end_page="1140" type="sub_section"> <SectionTitle> 3.1 A descriptive device </SectionTitle> <Paragraph position="0"> In a diMogue, sentences convey information about tim speakers' mental attitudes toward eventualities. This framework does not concern the mental attitudes, but focuses on the eventualities described in the sentences.</Paragraph> <Paragraph position="1"> An eventuality is written as a variant of the Davidsonian representation (l)avidson 1980; Vlach 1993). For example, the informational content of the eventuality of forwarding described by (s4) is written as follows.</Paragraph> <Paragraph position="2"> Symbols starting with a cN)ital letter represent constants and symbols starting witl, the ctmracter '*' represent varlahles. Symbol '~;' is an of)erator \[or conjunetkm. null Type(L',T) means that eventuality l,; is classified as a type T. t{.epresentation (rl) specifies the. eventuality, *e/l, that *agcntl tbrwards *objt to *rcepl at time *t\],. The agem, and tire object of forwarding are represented as variables, since they are zeropronominalized. Llcarcr(l') means that P is the hearer. In the above, the recipient of forwarding is identified with the hearer since it is specified by tire pronoun &quot;sochira&quot;, designating the hearer. In addition, ewmtuality *c:1 is non-st~d.ive.</Paragraph> <Paragraph position="3"> SpecchTimc(T) means that time 7' is the speech time, Tcmp\]Coeus(7 ') means that time T is in the temporal focus, and 7'Rel(l{, 7't,7:e) means that temporal relationship lg holds between time ~I'\] and 7). In this framework, temporal relationships are represented based on temporal logic proposed by Allen (1983) and times are treated as temporal intervals. In the above, time *tSl is before sl)eech time *GpJ since *Ill is specified by the past-tense morpheme &quot;ta&quot;. Time *tlo~.,t,t is in the temporal focus. Temporal relationship betweeen *Ill attd *l\]o~u,l is represented as a w~riable, *roll. Resolving temporal rel)rence means determining a relevant tentporal relationship betweeen *tit and *t\]ocu.,1.</Paragraph> <Paragraph position="4"> Knowledge of the temporal relationship between an ewmtuality and the existential status of individuals is represented as a triplet < \]~;R, {i\[~.,...},Tlg >, where 1,;1~ is a represent,ttion for the eventuality, {\[R,...} is a set of representations of the existen-.</Paragraph> <Paragraph position="5"> tial status of the individuals, and Tt~ is the teulporal relationship between them. This framework concerns the existential status of individuals such that an individual exists at a certain space-time location of the physical world. For example, knowledge about an eventuality of forwarding is written as follows.</Paragraph> <Paragraph position="6"> Loe(*x, *1) means that individual *x exists at lo..</Paragraph> <Paragraph position="7"> cation *l. in this dialogue domain, the location where an e-mail message exists is a mail box. Owner(,l, .p) means that person *p owns location */. I assulne here that the owner of a mail box is uniquely identified.</Paragraph> <Paragraph position="8"> /it the ahove, \[l~\]a specifies the existenti~fi status of *obj, whM1 is the object being forwarded, and says that *obj exists at time *to~j and at location *lobd, which the agent of forwarding owns. lleZb specifies the existential status of *copy, which is a copy of *obj aud is generated by forwarding *obj. The object thai; the recipient of forwarding receives is ,lot identified with *obj becmlse of domestic constraints concerning an e-mail system, lJgIi, says that *copy exists at time *tcopu and at lo('ation *le~py, which the recipient of forwarding owns. 3'lC/.j says that the time: of forwarding, *t j, must be during the time, *to,j, when .obj exists, and that the time of forwarding, *t: nmst be before the time, *tcopy, when *copy exists.</Paragraph> <Paragraph position="9"> l(nowledge about an eventuality of deletiug is written as follows.</Paragraph> <Paragraph position="11"> (\['led d(~t' ,\[,\[~el(Mect, *td, j, *td).</Paragraph> <Paragraph position="12"> l lgd says that the object being deleted, *oh j, exists at time *ld and at h)cation *loci owned by the agent of deleting, *agent. 7'lQ says that the time when ,obj exists must be immediately before the time of deleting.</Paragraph> </Section> <Section position="2" start_page="1140" end_page="1141" type="sub_section"> <SectionTitle> 3.2 Resolving temporal reference </SectionTitle> <Paragraph position="0"> This framework assumes that a representation of an eventuality described by a sentence is given, in the representation, pronominalized individuals an(l indeterminate teml)oral relationships are represented as variables such as *agent1 ~md *rOll in (rl). When the representation of the eventuality described by the current sentence is given, representations of the existential status of individuals and temporal relationships between the eventuality amt the existential status of individuals are derived by using knowledge such gm (r2) and (r3). These representations are interpreted within the context as described below. In the interpretation process, appropriate constants are substituted for variables. After the interpretation process, the representations are introduced into the context. Thus, the context includes representations of eventnalities, the existential status of individuals, and temporal relationships among the eventualities and the existential status of individuals that have been mentioned in a dialogue. In addition, it includes representations that show who is the speaker~ who is the hearer, what is the speech time, and what is the time in the temporal focus.</Paragraph> <Paragraph position="1"> Let RSet be a set of representations of an eventuality, E, described by a sentence, the existential status of individuals mentioned in E, and temporal relationships between them. The interpretation process is as follows.</Paragraph> <Paragraph position="2"> (I1) A representation, /~, in 12set is unified with a representation, R~, in the context, if possible.</Paragraph> <Paragraph position="3"> Through unification, constants in R~ are substituted for variables in/C (i2) An indeterminate temporal relationship between the time of eventuality E and the time in the temporal focus is identified with the relevant temporal relation according to default interpretation rules and transitive and reflexive laws governing temporal relationships.</Paragraph> <Paragraph position="4"> (I3) Constants are generated and substituted for variables that cannot be identified in steps (I1) and (I2) of this process.</Paragraph> <Paragraph position="5"> (I4) Representations in Rset are added to the context. Some nominal reference is resolved in (I1), although this paper does not go into how nominal reference is resolved.</Paragraph> <Paragraph position="6"> In (I2), temporal reference is resolved. The interpretation by transitive and reflexive laws governing temporal relationships is preferred over the interpretation by default interpretation rules.</Paragraph> <Paragraph position="7"> This framework uses the defanlt interpretation rules (R1) and (R2), which are used in existing models. The default interpretation rules (R1) and (R2) are represented as the following theorems, (r4) and In the above, R1 D R2 means that RI implies R> The transitive and reflexive laws governing temporal relationships are also represented as theorems. For brevity's sake, I will not present all the laws. Allen (1983) presents a exhanstive list of transitive SHare i ignore conditions where the eventualities at stake are past ones.</Paragraph> <Paragraph position="8"> laws governing temporal relationships. The following theorems are sufficient for dealing with dialogue (dl). (r6) T~el(1)u,'i~q, **, *z)~7','el(M~< *~, *V) Trel(Befove, *x, *y).</Paragraph> <Paragraph position="9"> (r7) Trel(t3efore, *x, *y) D Trel(After, .y, .x).</Paragraph> <Paragraph position="10"> (rS) T~el(D,m.g, **, ,y) ~ :C~l(Co.~,i..~, w, *~). The interpretation by the transitive and rellexive laws governing temporal relationships can be regarded as a kind of of knowledge-based interpretation as described in sec. 2.1, although only a restricted set of world knowledge is used in this framework. As demonstrated in see. 4, the interaction between references to individuals and times plays an important role in resolving temporal reference according to the transitive and reflexive laws governing temporal ,:elationships.</Paragraph> </Section> </Section> <Section position="6" start_page="1141" end_page="1143" type="metho"> <SectionTitle> 4 EXAMPLES </SectionTitle> <Paragraph position="0"> This section demonstrates how the framework works by using sentence (s4) and (s5) as examples. First, consider the interpretation of (s4) under the context established by (s2). Sentence (s2) introduces an eventuality of deleting, Ed, into the context. The eventuality is represented as follows.</Paragraph> <Paragraph position="1"> in (rg), M represents an individual, which is an e-mail message, Td represents the time of Ed, and ?\['~p represents the time when sentence (s2) is uttered. 9 By using knowledge (r3), the existential status, Era, of M and the temporal relationship between Ed and Em are derived and introduced into the context.</Paragraph> <Paragraph position="2"> They are written as follows.</Paragraph> <Paragraph position="3"> Tm represents the time when the e-mail message M exists and L,~ represents the location of M.</Paragraph> <Paragraph position="4"> The context also includes the following representation when (s4) is interpreted.</Paragraph> <Paragraph position="5"> (r12) Speaker( John)&llearer(13ill).</Paragraph> <Paragraph position="6"> (r 13) Spa e chTime ( T,p )& 7'e mp F ocus'( Td). Namely, I assume that the time of deleting~ Td, is in the temporal focus when (s4) is interpreted.</Paragraph> <Paragraph position="7"> Now, let me explain how sentence (s4) is interpreted under the above context. Sentence (s4) describes an eventuality of forwarding, *ell , which is written ~ representation (rl) described in sac. 3.1. Likewise, by using knowledge @2), the following representations are derived.</Paragraph> <Paragraph position="8"> In (rl), *agentx, *rc.cpl and *objl represent respectively the pronominalized agent, recipient, and object of fbrwarding. Variable *reep~ is identified with Bill by ,rallying \[learer(*recp~) in (rl) with (r12) in the coutext.</Paragraph> <Paragraph position="9"> Representation (r14) is unified with (rl0), ~deg and then *ayent~ is identified with John and *obj\] is identiffed with M. Likewise, *eobj ~, *lobj~, and *to~j~ are identified respectively with Era, Lm and {g,,.</Paragraph> <Paragraph position="10"> Consequently, nominal reference in sentence (s4) is resolved. As stated below, identifying *obji with 3//serves to resolve temporal reference.</Paragraph> <Paragraph position="11"> By using (r13), variables, *t,~)~ and *tf ..... 1 are identitied respectively with T.~ v and 7'd.</Paragraph> <Paragraph position="12"> The following temporal relationship is deriw;d fi'om (r16) bee~mse *objl is identitied with M and then *tobjl is identified with &quot;/;,~.</Paragraph> <Paragraph position="13"> (r18)Tltel( I)uring, ,ti~, 7;,).</Paragraph> <Paragraph position="14"> The tbllowing temporal relationship is derived t.'1&quot;o111 (rl) because *t\]o~,.,~ is identitied with 7'd. (r l 9 ) T \[eel( *rel , , *t \], , Td ).</Paragraph> <Paragraph position="15"> Resolving temporal reference here means determining temporal relationship *tel, in (r19). By default interi)retation rule (r4), the tbllowing representation is derived from (r19).</Paragraph> <Paragraph position="16"> (r20) 7'ted(After, *t \] ~ , :l a ).</Paragraph> <Paragraph position="17"> On the other hand, by applying theorem (r6) to (r19) and then using (r18)and (r\]l), the following represent~tion is derived.</Paragraph> <Paragraph position="18"> (r21) :l'~.d Utefo,&quot; <*t\]\], &quot;~'~).</Paragraph> <Paragraph position="19"> Knowh;dge..based interpretation (r21) is preferred over default interpretation (r20). Consequently, the relevant temporal relationship between forwarding and deleting is determined.</Paragraph> <Paragraph position="20"> Finally, new constants IQ, 7:t, l'.'~o~,a, Copy, L~ovy, and %.opy are generated for respectively variables *d,tl, *t\]l, *eoop,al, *copy\], *lC/opvl, and *t~.opul. Constant Copy represents the copy of the e-mail message M, generated by forwarding M. l,'inally, the following representations are introduced into the context.</Paragraph> <Paragraph position="21"> Next, consider the intm:l)retation of sentence (sS), which describes the R)llowing eventuality, *e.,:2.</Paragraph> <Paragraph position="23"> Here, I assume that (s5) directly describes the existentiM status of an individual *obj.e, which is realized as the zero-pronomlnalized subject in the sentence, mid that the existential status is construed as a stat, ive eventuality. '\['he location, *l,,2, of *obj.e is specilied as a mail box that the hearer owns since the location is designated hy &quot;sochira no mail 1oox (your mail box)&quot;.</Paragraph> <Paragraph position="24"> The time, *t.,.~, when *obj.e exists is before the speech time since the past-.tense morpheme &quot;ta&quot; is used.</Paragraph> <Paragraph position="25"> '\['he referent for *obj.2 is mnbiguous since the refer cnt can be either e-mail message M or its copy Copy.</Paragraph> <Paragraph position="26"> The relewmt reDrent muss he Copy. As argued below, resolving this nominM reibrence is crucial in resolving temporal reference.</Paragraph> <Paragraph position="27"> I assume that the time of forwarding, 7}, is in the temporal focus. Resolving temporal reference here means dete.rmining temporal relationship *tel2 t)e~ tween *t,2 and ~/}. The relevant interpretation is th{~t * t~.~ is after illt.</Paragraph> <Paragraph position="28"> Let me explain how the fi'amework interprets (sS).</Paragraph> <Paragraph position="29"> First of all, *person in (r26) is identified with Bill, since *person nmst be the hearer. '\['hen *%2 in (r26) is identitied with E~ovy in (r23). Likewise, *obj.e, *l,~u, and *t~.u are identified respectively with Copy, L~ovy, and Teovv. Thus tim zero-pronominalized subject is appropriately interpreted. As a result, the following temporal relationship is derived from (r26) since *t:,,p.</Paragraph> <Paragraph position="30"> is identified with &quot;l'~ovy and 7} is in the temporal focus. 0,27) 7 'Ied (*,'d~, :I'~o,,,~, '.l) ).</Paragraph> <Paragraph position="31"> llere, consider how the temporal relationship *tel2 is determined. By using default interpretation rule (rS), *rel.e is identilied with a relatkm, Contains, since the eventuality described by(s5) is stative.</Paragraph> <Paragraph position="32"> On the other hand, by using (r25) and theorem (rT), *rel.e is identified with a relation, After. In other words, the time of the eventuality deseribe.d by (sS) follows the time of forwarding. This knowledge-based interpretation is l)referred over the default in-terpretation, and is the relevant interpretation.</Paragraph> <Paragraph position="33"> In the above process, identifying the pronominalized subject, *obj2, of (sS) with Copy is crucial for the temporal reference resolution. Assume that *obj~ is identified with the e-mail message M. This case happens when *ex2 in (r26) is identified with E,~ in (rl0) and *t~2 is identified with 7~. In this case, the following temporal relationship is derived from (r26).</Paragraph> <Paragraph position="34"> (r28)T~el(.rel~, Tin, T~).</Paragraph> <Paragraph position="35"> By using (r24) and theorem (r8), *rel2 is identified with a relation, Contains. This interpretation is not relevant.</Paragraph> <Paragraph position="36"> However, the case that leads to the wrong interpretation never occurs. When *e~2 is identified with Era, the following representation is derived from (r26) since *person is identified with Bill.</Paragraph> <Paragraph position="37"> (r29) Loc( Em , *l~. 2 )&Owner( *l~ 2 , Bill).</Paragraph> <Paragraph position="38"> This representation is inconsistent with (rl0) since the owner of the location of the e-mail message M must be uniquely identified. Thus, *e~.2 must be identified with E~opy and then *obj2 must be identified with Copy.</Paragraph> <Paragraph position="39"> Consequently, identifying appropriately the referent of the pronominalized subject of sentence (s5) affects the process of resolving temporal reference, and this reference interaction can be explained by exploiting knowledge such as (r2) and (r3).</Paragraph> </Section> class="xml-element"></Paper>