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<Paper uid="C96-2132">
  <Title>Zero Pronouns and Conditionals in Japanese Instruction Manuals</Title>
  <Section position="3" start_page="782" end_page="783" type="metho">
    <SectionTitle>
2 Zero pronouns in manual
sentences
</SectionTitle>
    <Paragraph position="0"> Let's consider the following Japanese sentence,  which shows a certain instrnction. (1) C/~, kono-botan-o osu -to, (~a-N()M this-button-ACe push -TO  C/b der -are -mas -u.</Paragraph>
    <Paragraph position="1"> qSb-NOM go ollt -car |-I'Ol,-NONPAST. If lb, push(es) this button,then C/b can go oul.. Native speakers of Japanese have the following intuitive interpretation for (1) without any special context.</Paragraph>
    <Paragraph position="2"> (2) C/. : = the hearer (= the u, er) Here, 'TO' is a Japanese conjunctive particle which represents a causal relation. 'MASU' shows politeness, Milch is expressed by cot, iu(l). The 'ARE' shows ability or permission.</Paragraph>
    <Paragraph position="3"> On the other hand, the following sentence, which does uot have the verbal suffix of possibility 'ARE' in the matrix clause, has a different interpretation.</Paragraph>
    <Paragraph position="4">  (3) C/c kono-botan-o osu -to, (~c-N()M this-button-Ace push -TO,  Ca de -mas -u.</Paragraph>
    <Paragraph position="5"> q~d-NOM conic out -POL -NONPAST. 1 If C/C/ push(es) this button, then Ca will come out.</Paragraph>
    <Paragraph position="6"> The zero pronoun Ca does not refer to tim hearer(the user), even though qS~ refers to the user as well a.s (1). The intuition of native sl)eal~ers of Japanesc for (3) is that Cd refers to a machine or a certain part of the machine. Note that when only the matrix clause of (3) is use(t as shown in (4), C/,. can lie interpreted as either the hearer or the  machine ~, (4) gb e de -lnas-u.</Paragraph>
    <Paragraph position="7">  (/)e-NOM go out -POl, -NONPAST.</Paragraph>
    <Paragraph position="8"> C/~ will go out.</Paragraph>
    <Paragraph position="9"> These examples show that the expressions TO and ARE impose some constraints on the referents of SUBJECTS of the sentences. As described above, there are many cases that linguistic expressions give us a key information to resolve some tyl)e of ambiguity like the a.nal)hora of a zero pronoun. In the rest of this paper, we will show several pragmatic constraints, which can aceonllt for the in terpretations of these sentences described above. I)ohsaka(l)ohsaka, 1994) l)roposes a similar approach, in which pragmatic constraints are used to determine rethrents of zero pronouns. While his apl)roach treats dialogue, our targets are manual sentences. His approach utilizes honorific expressions and the speaker's point of view. Since the constraints are efl'ective in the (lifferent target from ours, the accuracy of identifying the referents of zero pronouns would be improved much more by using both of his constraints and the constraint we proposed. As for the identifying method available in general discourses, the centering theory(Brennan et al., 1987; Walker et al., 1990) and the property sharing theory(Kameyama, 1988) are proposed. Although this kind of theory has a good point that it is independent of the type o17 discourse, the linguistic constraints specitic to expressions like the pragmatic constraints l/roposed  by Dohsaka or us are more accurate than theirs when the speeitlc constraints are applicable. 3 General ontology in manuals and prinmry constraints  In this section, we consider the general ontology which can be used in ,dl types of manuals. We shouhl consider two types of information as the parts of ontology: the properties of the objects in manuals and the discourse situation that is characterized by linguistic roles like a writer and a reader.</Paragraph>
    <Paragraph position="10"> Constraint 1 (Objects) User has intention.</Paragraph>
    <Paragraph position="11"> Manutheturer has intention.</Paragraph>
    <Paragraph position="12"> Machine has no intenlion.</Paragraph>
    <Paragraph position="13">  ferent from the translation ill (1). It is due to the ditference of tile viewl)oint be.tweei, Japanese and Eliglish. The difference has no effect on the selection of zero prOllOllll~S refercllt.</Paragraph>
    <Paragraph position="14"> 2It seems to be more natural that Ce is interl)reted as the hearer.</Paragraph>
    <Paragraph position="16"> From these constraints of the ontology, we can obtain the constraint of persons as follows.</Paragraph>
    <Paragraph position="17">  Before considering the constraints of Japanese conditionals, we had better mention the more basic expressions in manuals. In Japanese, simple operation procedures, like those which do not inelude some conditions, are often described as simple sentences with no subjects whose verbs arc of one of the following types: the RU form, the request form or the solicitation form. The RU form is the basic form of verbs and it denotes the non-past tense. Since the RO form has a neutral meaning, it does not impose any restriction on the SUBJECT.</Paragraph>
    <Paragraph position="18"> On the other hand, the request form and the solicitation form have some constraints. The speaker uses the sentences to prompt hearers to do an action described by the sentence. Therefore, we have the following constraint.</Paragraph>
    <Paragraph position="19"> Constraint 4 (SUBJECT of sentence in the request form) The SUBJECT of a sentence in either the requesl form or the solicitation form is the hearer, Manual sentences may have a kind of modality expressing the permission, the possibility, the obligation, and so on. Sentences which have the expressions of ability or permission mean not. only that it is possible for the SUBJECT of the sentence to do the action, but also thai; the SUBJECT has their choice of whether to do the action or not to do it. Therefore, we have the following.</Paragraph>
    <Paragraph position="20"> Constraint 5 (SUBJECT of sentence with ability expressions) A SUBJECT of a sentence with the expressions of ability or permission must have his~her intention to make a choice about the action described by the .sentence.</Paragraph>
  </Section>
  <Section position="4" start_page="783" end_page="786" type="metho">
    <SectionTitle>
4 Semantics of Japanese
Conditionals
</SectionTitle>
    <Paragraph position="0"> Japanese has four conditional particles, TO, REBA, TARA and NARA, which are attached to the end of subordinate clauses as described in (1). The subordinate clause aud the matrix clause conjoined by one of these particles correspond to the antecedent and the consequence, respectively. Each expression has its own meaning as shown in Table l(Masuoka, 1993). TARA and NARA are very rarely used in manual sentences as far as we examined. For example, the rates of use of each conditional in over a dozen of instruction manuals are as follows3: TO is 77.6 % (385 sentences) of all conditionals, REBA is 19.4 % (96 sentences), TARA is 2.6 3As described later, we have examined several other manuals especially for the consideration of the % (13 sentences) and NARA is 0.4 % (2 sentences).</Paragraph>
    <Paragraph position="1"> Roughly speaking, TO and REBA show causality relations, namely some general rules, and TARA and NARA are used in the case that the the antecedent is an assumption. The fact that not assumptions but general rules are usually described in the context of instruction is the reason why TARA and NARA are used less fi'equently than TO and REBA.</Paragraph>
    <Paragraph position="2"> The difference of constraints of these expressions are shown in the following sentences, which are the variants of the sentence (3).</Paragraph>
    <Paragraph position="3">  out/go out.</Paragraph>
    <Paragraph position="4"> As well as the sentence (3), for Japanese native speakers, the SUBJECT of the matrix clause of (5) should be a machine. On the other hand, in the case of the sentences (6) and (7), the SUBJECTS of the matrix clauses can be either users or ma(:hines. These phenomena probably due to the nature of each conditionals. Since a causal relation, which is shown by TO or REBA, expresses a general rule, the consequence cannot include speaker's attitude, like volition and request. Therefore, the SUBJECT of the matrix clause should be a machine. In contrast, in the case of assumptions, that is TARA and NARA , there are no such restrictions on the SUBJECT .</Paragraph>
    <Paragraph position="5"> It depends on the volitionality of the verb whether a sentence shows a speaker's attitude, or not. Therefore, we consider each Japanese conditionals in terms of volitionality of the verb. Note that the electronic dictinary IPAL provides the information of volitionality for each Japanese verb entry(IPA Te.chn01ogy center, 1987). We can use it to analyze sentences based on our proposal.</Paragraph>
    <Section position="1" start_page="783" end_page="784" type="sub_section">
      <SectionTitle>
4.1 SUBJECTS of complex sentences with
</SectionTitle>
      <Paragraph position="0"> the eonditional TO A matrix clause of the sentence with TO expresses a consequence of a causal relation. Consequently, conditionals REBA , TARA and NARA, since they occur less frequently than TO in manuals and we have to collect more examples to estimate their property in nralluals.</Paragraph>
      <Paragraph position="1">  shows successi{;eness of two&amp;quot;e;eents observed in a real situation. shows a universal causal relation. ' .....</Paragraph>
      <Paragraph position="2"> It becomes more assurnlStive when the subordinate clause shows a state. shows l) two individual events occur with ~ie l)assing of tile time, or 2) an event which is expected to occur on the uncertain assumption expressed in the subordinate clause.</Paragraph>
      <Paragraph position="3"> shows that the antecedent of the senl.e.nce is an ~ssumpi, i0n ..... and tire consequence holds on that ;~ssmnption.</Paragraph>
      <Paragraph position="4"> in matrix clauses, we can use either the mood of the description of fa.cts or the mood of evidentials like conjectures, judgment and so on. In contrast, we may not use the expressions of volition, requests and so on. We consider only the mood of the description of facts, because manual sentences should describe only facts and must not in('ludc sl)eaker's at, titude. The sentences having the mood are classified into two types: tile (lescription of an action and the description of a state like an expression for the ability of some action.</Paragraph>
      <Paragraph position="5"> The former type is problematic, because the RUl'orm~ which is the normal inflection form of verbs and describes an action, is ambiguous in its meaning. The RU-fonn can show one of tit(', followings: speaker's volition, speaker's request t,o hearers, or the action done hy a third party.</Paragraph>
      <Paragraph position="6"> In the analysis of the description of an action, it, is important to examine whether the verb phrase expresses a volitional action or not. According to the classitlcation by IPA(IPA Technology eenter, 1987), all of Japanese verbs are classitied into two types, volitioual verbs, which usually express int, entional actions, and non-volitional verbs, which express non-intentional actions. Although non-volitional verbs only exl)ress non-volitional actions, volitional verbs are cb~ssitied into two kind of verbs. One is the type of verbs which can be used tbr not only volitional actions but also non-volitional actiorts. The other is the type of verbs which are used only for volitional actions. For example, ITAMO(havc a pain) is a non-volitional verb, OTOSO(drop/loose) is a volitional verb which has also the non-volitional use, SAGASU(scarch) is a volitional wM) which has only the volitional use.</Paragraph>
      <Paragraph position="7"> Let us consider the interpretations of the ma-trix clauses of the sentences with 1-O. The first case is that verbs in the matrix clauses are in volitional use. If the SUBJECT is the speaker, the verb in volitional use expresses speaker's volition. If the SUBJECT is the hearer, the st)eaker expresses his/her expectation that the hearer makes a volitional action shown by the sentence. This is the case of requests. Consequently, the SUBJECT should be neither the speaker nor the hearer due to the constraint that we cannot express sortie volition o1: request in a matrix clause of the TO sentence. On the other hand, a third paJ'ty can 1)e the SUBJECT, because a sentence whose SUBJECT is a third party does not express any volition, invitations, requests or injunctions. Since tile manufactm'e is the speaker and the user is the hearer according to the constraint of the discourse situation, the mauufacture Ltll(l tile user cannot be the SUBJECT of the matrix clause. Therefore, the only possible interpretation is that the SUBJECT of the matrix clause is the machine.</Paragraph>
      <Paragraph position="8"> The second case is thal, verbs in the nlatrix clauses are in nell-volitional use. If a verb of the matrix chmse has a non-volitional use, thai, is, it' it is possible for the action of the clause to be done unconsciously, the constraint is not applied, because the w:rb in non-volitional use does not express any volition, invitations, requests and im junctions. For example, the SUBJECT of the matrix clause of the following sentence refers to the users.</Paragraph>
      <Paragraph position="10"> \[1'@ touch(es) qSq, then 4h will get an eh'.etric shock.</Paragraph>
      <Paragraph position="11"> To examine the accuracy of interpretations bused on our estinmtion we have collected about 400 sentences, which include TO and some of which also inch.Me possibility expressions, from several types of inanuals, l/y these sentence.s, we check Constraint 5 and our estimati(m of TO. Then, it is contirmed that there are no excel)tion to them, at least in the collected sentences.</Paragraph>
    </Section>
    <Section position="2" start_page="784" end_page="786" type="sub_section">
      <SectionTitle>
4.2 SUBJECTS of comI)h~.x s(mten('es with
</SectionTitle>
      <Paragraph position="0"> the conditionals REBA,TARA and NARA Because of the characteristics of each conditionals descril)e(t in Table 1, we expect that a) the conjunctive REBA, which shows a causal relation, has the same constraint as TO has, which also express causality, b) since both of TARA and NARA express an assumption, they have the same type of constraint, which is difl'erent fi'om the constraint of TO and REBA. As the first step to confirm this expectation, let us examine whether the matrix clause may have a request form, or not, in the cruses of REBA,TARA and NARA. At lirst, note that the hearer, namely the use.r, is the agent of Cite requested action if the matrix clause is a. re(luest form. In the case that the conjunctive shows causality, the matrix chmse should show some inevitable result of tile event expressed by the  subordinate clause. Therefore, tile matrix clause should not express the judgement and attitude of the speaker. As for the conjunctive REBA, the fact that tile conjunctive represents some causality means that the matrix clause does not have a request form. Note that the exception is tile case that the subordinate clause is stative, or a non-volitional action. As described in 'Fable 1, in those eases, the subordinate clause shows an assumption rather than a cause, and the matrix clause may be a request as shown in the following example.</Paragraph>
      <Paragraph position="1">  If there is no need of Cp, please discard Cp.</Paragraph>
      <Paragraph position="2"> The usages of the conjunctives TARA and NARA, which express assumptions, are explained as follows. Since the assumptions are introduced by the speaker, the matrix clause is to describe speaker's expectation or desire. Therefore, it is quite probable that not only the normal form but also some request form, which is considered as a kind of wish, appears in the matrix clause.</Paragraph>
      <Paragraph position="3"> In order to ascertain our estimation, we have examined a bunch of real sentences, which appear in real instruction manuals. First of all, in about 400 TO sentences, all of tile matrix clauses have no request form. In the REBA case, few request form appear in the matrix clauses. The exceptions are the same type of sentences as (9).</Paragraph>
      <Paragraph position="4"> Next, we consider the usage of TARA and NARA.</Paragraph>
      <Paragraph position="5"> Even if the conjunctive REBA in the sentence (9) is changed for TARA or NARA, the sentences are still acceptable. As we exepcted, it shows that the matrix clause of the sentence with TARA or NARA may have a request form, that is , the SUBJECT of the matrix clause may be a user. Then, can the SUBJECT of the matrix chmse be a machine? We expect that there are few cases that the SUB-JECT of the matrix clause is a machine, because the highly context specific assumption, which is expressed by TARA or NARA, is not suitable for tile description of general rules. Moreover, fi'om the fact that the matrix clause of TO and REBA cannot express the speaker's attitude, we pragmatically infer that TARA and NARA are expected to be used only for expressing the speaker's attitude. Our expectation is summarized in Table 2. Note that a SUBJECT should be either a user or a machine because manufacturers have finished all the actions appeared in the context of instruction before shipment.</Paragraph>
      <Paragraph position="6"> Our estimation about TO has been already confirmed in Section 4.1. In order to confirm our estimation about REBA,TARA and NARA, let us examine real examples. Since tile constraints we pursue here are those which restrict the types of SUBJECTS, we examined the correlation among the types of conjunctives, the types of verbs and the SUBJECT. As for the types of SUBJECTS, a SUBJECT should be either a user or a machine.</Paragraph>
      <Paragraph position="7">  As for tile types of verbs, each clause is classified into two classes according to volitionality of verb. One of them is tile cl;~ss of verbs in volitional use, the other is the class of other non-volitional predicates. Therefore each clause belongs to one of the followings:  of each conjunctive. Each number shows the frequency of use in the examples we examined. Note that to create 'Fable 3,4 and 5, several Japanese native speakers determine referents of zero SUBJECTS according to contexts.</Paragraph>
      <Paragraph position="8">  First of all, as we expected before, the distribution of the use of REBA is different from those of TARA and NARA. While we call see several differences of use, the most remarkable one is the difference of use of the matrix clause. The matrix clauses of REBA are hardly any user's volitional action. The exceptions are only about 5% of all examples. The distribution of use of the matrix clauses of TARA and NARA is complementary to the distribution of REBA, that is, the majority of the matrix clause of TARA(about 90% of all examples) and NARA(100% of all examples) are user's volitional actions, although the number of the total examples of NARA is not so numerous. The empirical result supports the our estimation.</Paragraph>
    </Section>
    <Section position="3" start_page="786" end_page="786" type="sub_section">
      <SectionTitle>
4.3 Default rules of usage of REBA, TARA
</SectionTitle>
      <Paragraph position="0"> and NARA The tendency of use of the conjunctives gives us a couple of strong defimlts to resolve the zero pronoun in tit(; matrix clauses. We propose the following defaults.</Paragraph>
      <Paragraph position="1"> Default 1 (SUBJECT of sentem:e with TO or</Paragraph>
    </Section>
  </Section>
  <Section position="5" start_page="786" end_page="786" type="metho">
    <SectionTitle>
REBA)
</SectionTitle>
    <Paragraph position="0"> In a complex sentence with the connectzve particle TO orREBA, the matrix clause does not empress user's volitional action. Therefore, the SUBJECT of the matriz clause should be a machine, if the verb of the matrix clause does not have the non-volitional use.</Paragraph>
    <Paragraph position="1"> Default 2 (SUBJECT of sentence with TARA or NARA) In a complex sentence with. the connective particle TARA or NARA, the matrix clause e~:presses only user's volitional action. 7'h.erefore, the SUB-JECT of the malrix clause should be a user. The accuracy of the default rules of -I-O,REBA,TARA and NARA is 100%, 95.1%, 89.8% and 100%, respectively, as far as we examined.</Paragraph>
  </Section>
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