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<?xml version="1.0" standalone="yes"?> <Paper uid="C92-1043"> <Title>ACTION RELATIONS IN RATIONALE CLAUSES AND MEANS CLAUSES*</Title> <Section position="4" start_page="0" end_page="0" type="metho"> <SectionTitle> ACRES DE COLING-92, NANTES, 23-28 h0~r 1992 2 6 7 </SectionTitle> <Paragraph position="0"> least in part, these two challenges. As their names suggest, means clauses express the means by which an action is performed, while rationale clauses express the reason, or rationale, of the main clause action. In the last section of this paper, we show how to distinguish rationale clauses from two superficially similar constructions: purpose clauses, as in &quot;Mary bought a suit to wear at the meeting&quot;, and infinitival relative clauses, as in &quot;John found the book to give to his sister&quot;. null (1) ~. Mary pressed the button to reset the printer.</Paragraph> <Paragraph position="1"> b. Mary reset tbe printer by pressing the button.</Paragraph> <Paragraph position="2"> Rationale clauses and means clauses are of interest not only as exemplars of multi-action utterances, but also because of the subtle differences in the information that can be felicitously inferred from their use. For example, despite the similarities between (la) and (lb), the continuation in (2), below, is felicitous after (la) but not after (lb). The interpretation task therefore requires determining the relations between the actions described in multi-action utterances and drawing appropriate inferences about them. This particular need is one of the issues addressed in this paper.</Paragraph> <Paragraph position="3"> (2) But that didn't work because she forgot to plug it in. We start by presenting distinctive properties of utterances with rationale clauses and means clauses. After describing their logical form, we then present the generation, enablement and Contributes relations between actions \[3, 13\], arguing for their use in the interpretation of these constructions. We finally define interpretation rules for deriving the meaning of the logical form predicates representing means clause and rationale clauses. We also show how these rules predict the properties of these constructions mentioned above. We end the paper by discussing the scope of the analysis and showing how the constructions to which these rules apply can be distinguished algorithmically.</Paragraph> <Paragraph position="4"> A companion paper \[5\] examines the mental states of the speaker and performing agent of such utterances, and describes the interpretation model.</Paragraph> </Section> <Section position="5" start_page="0" end_page="0" type="metho"> <SectionTitle> 2 Properties of rationale and </SectionTitle> <Paragraph position="0"> means clauses A detailed analysis of multi-action utterances in task-oriented dialogues \[3\] and a subsequent examination of a set of selections from the Associated Press news wire Pace. OF COLING-92, NANTES, AUG. 23-28, 1992 revealed the following distinctive features displayed ill utterances with rationale clauses and means clauses.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 2.1 Semantic properties </SectionTitle> <Paragraph position="0"> Overlap: In utterances with means clauses or rationale clauses, the performance of one of the actions referred to in the utterance may result in the simultaneous performance of the other (but need not, see below). The overlap in meaning between utterances (la) and (lb) exemplifies this property: in both utterances, Mary's pressing the button may result in her resetting the printer at the same time.</Paragraph> <Paragraph position="1"> Distinction: It follows from past tense utterances with means clauses, but not from those with rationale clauses, that the agent's &quot;goal action&quot; was successfully performcd. This action is described in the main clause of an utterance with a means clause, but in tim adjunct clause of an utterance with a rationale clause.</Paragraph> <Paragraph position="2"> This property is reflected in tbe difference between utterances (la) and (lb) with respect to tile continuation in (2): only from (lb) can it be concluded that Mary successfully reset the printer 1. Thus (2) is not felicitous in the context of (lb), but it is in that of (la) because in that context, Mary might have failed to reset the printer.</Paragraph> <Paragraph position="3"> Ambiguity: Utterances with rationale clauses are ambiguous with respect to the relative timing of the two actions referred to: the performance of the main clause action may result in the simultaneous performance of the adjunct clause action, or it may only make possible its subsequent performance. This prop-erty explains why, in the examples helcw, response (3b) is felicitous whereas the same utterance in tile context of (4a) is not.</Paragraph> <Paragraph position="4"> (3l a. John: I inserted a diskette to back up my file.</Paragraph> <Paragraph position="5"> b. Mary: Okay, now back up the file.</Paragraph> <Paragraph position="6"> (4) a. John: I typed 'cp new.txt' to back up my file.</Paragraph> <Paragraph position="7"> b. Mary: * Okay, now back up the file.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 2.2 &quot;Algebraic&quot; properties </SectionTitle> <Paragraph position="0"> I)rawing an analogy with the algebraic properties of relations, utterances with means clauses and rationale clauses are irreflexive, asymmetric and transitive, a~s reflected in the following examples (the first utterance or utterance pair of each set includes a means clause, th,' second, a rationale clause).</Paragraph> <Paragraph position="1"> I',l a.*Mary reset tile printer by resetting the printer. *Mary reset the printer to reset the printer.</Paragraph> <Paragraph position="2"> b. Mary reset the printer by pressing the button.</Paragraph> <Paragraph position="3"> *Mary pressed the button by resetting the printer.</Paragraph> <Paragraph position="4"> Mary pressed the button to reset the printer.</Paragraph> <Paragraph position="5"> *Mary reset the printer to press the button.</Paragraph> <Paragraph position="6"> c. Mary fixed her problem by resetting the printer by pressing the button.</Paragraph> <Paragraph position="7"> Mary fixed her problem by pressing the button.</Paragraph> <Paragraph position="8"> 1 The companion paper \[5\] addresses the issue of embedding inferences like this one in belief contexts.</Paragraph> <Paragraph position="9"> Mary pressed the button to reset the printer to fix her problem.</Paragraph> <Paragraph position="10"> Mary pressed the button to fix her problem.</Paragraph> <Paragraph position="11"> Similar examples may be found to show that utterances with rationale clauses about sequential actions have tile same properties, e.g., for transitivity: (6) John borrowed the book to bring it back lmlne.</Paragraph> <Paragraph position="12"> John brought the book back home to look for papers on adjunct clauses.</Paragraph> <Paragraph position="13"> John borrowed the book to look for papers on adjunct clauses.</Paragraph> <Paragraph position="14"> Transitivity affects utterances with means clauses and rationale clauses in different ways. The transitivity of utterances with means clauses, illustrated in the first utterance pair of (5c), makes it possible to describe actions at lower levels of detail, i.e., with greater granularity. The transitivity of utterances with rationale clauses, and in particular those that describe sequential actions as illustrated ill (6), increases not tile granularity of the description, but the &quot;distance&quot; between tile actions described, i.e., the number of steps in tile sequence of actions linking them.</Paragraph> </Section> </Section> <Section position="6" start_page="0" end_page="0" type="metho"> <SectionTitle> 3 Actions and action relations </SectionTitle> <Paragraph position="0"> in logical forms Logical forms represent the literal meaning of all utterance and are derived cornpositionally by semantic interpretation rules based on the syntactic structure of tlre utterance. Our logical forms are be.sed on Davidson's formalism \[6\], because action reification facilitates the representation of utterances about multiple actions and relations among thent. These logical forms are existentially quantified sentences of first-order logic, with predicates that include all additional argument position for the action being described. Davidson's framework is extended for nmltiaction utterances by introducing multiple action variables and by representing connectives like &quot;hy&quot; (introducing means clauses) and &quot;to&quot; (introducing rationale clauses) using two-place predicates ranging over these action variables, as illustrated in (7) ~.</Paragraph> <Paragraph position="1"> (7) a. Mary reset the printer by pressing the button.</Paragraph> <Paragraph position="2"> LF: Sz~, x2, reset(zj ) h past(xl ) A ayt(x~, Mary) Aobj(xl, Printer) A by(x1, x2) Apress(x~) A obj(x,z, Button) b. Mary pressed the button to rcsct the printer.</Paragraph> <Paragraph position="3"> LF: 3xl,x2,press(x~ ) A past(xl) A agt(xl,Mary) Aobj(x,, Button) A i ..... der_to(z,, x~) ^ .... t(x:) ^ obj(x2, Printer) The following subsections discuss the four main components of these representations: action variables 2Extensional representations of propositions, like this one, have difficulties with respect to certain intensional phenomena sucb as substitution of identicals. Hobbs discusses this problem and a number of possible solutions Ill)l, but these questions lie beyond the scone of the nresent paner.</Paragraph> <Paragraph position="4"> AcrEs DE COLING-92, NANTES, 23-28 Aot~'r 1992 2 6 8 PROC. OF COLING-92, NANTES, AUG. 23-28. 1992 (e.g., xl and x2), action descriptions (e.g., tile predicates reset and press), tense predicates (e.g., tile predicate past), and action relations (e.g., the predicates by and in_order_to).</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 3.1 Action variables </SectionTitle> <Paragraph position="0"> While Davidson's formalism assumes that action variables denote &quot;reM&quot; action tokens, action variables in our formalism correspond to action entities in the discourse model. The ability to refer to an entity anaphorieally has been suggested as a test for &quot;discourse entity hood&quot; \[')0\]. Actions referred to in means clauses and rationale clauses pass this test, as illustrated in (8). The pronoml 'that' in this utterance is ambiguous, but the possibility of its coreferring with the adjunct clause action is sufficient justification for attributing discourse entity-hood to that action.</Paragraph> <Paragraph position="1"> (8) Mary will clone the rhinovirus to make a vaccine for the connnon cold and that will make her famous.</Paragraph> <Paragraph position="2"> Action entities may represent actual, or &quot;real&quot;, actions, i.e., actions that have occurred (e.g., the reset action in (7a)), or unrealized actions, i.e., actions that have not yet occurred or might never occur (e.g., the reset action in (7b) that may or may not result froln the press action) \[4\]. Quantification in the logical form is therefore over a universe that contains everything that can be talked about, with no commitment to existence ill the real worhl (as in, e.g., \[10, 17\]).</Paragraph> <Paragraph position="3"> Discourses in collaborative settings often involve discussions about unrealized actions. Agents, for exampie, might make suggestions for future actions, or dis cuss the advantages and disadvantages of a particular course of action. It is thus crucial to adopt a representation that will account for these actions as well.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 3.2 Action descriptions </SectionTitle> <Paragraph position="0"> Actions arc rcprescntcd by predicates taking a single action variable, e.g., reset(x)), and every action ar gmncnt is rcprescntcd by a scparate predicate, e.g., agt(xl,Mary). This type of representation has been proposed by a number of researchers (e.g., \[21\]) as an alternative to Davidson's representation, in which only the optional arguments arc represented as separate predicates. One reason is the arbitrariness that is sometimes involved in deciding on thc argument structure of various action predicates. For the present analysls, this type of representation is usefld because it avoids having either to introduce existential variables for missing arguments or to determine how these arguments are recovered during the process of building tile logical form. Missing subject and time arguments of adjunct clause actions in tile logical forms of means clauses and rationale clauses (e.g., those in (7)) can he recovered through the interpretatk)n of the action relations (see Section 5.2). Not all rationale clauses.</Paragraph> <Paragraph position="1"> however, \[lave empty subject positions, e.g., &quot;Mary prepared lobster (in order) for her gnests to have a taste of New Enzland cuisine.&quot;</Paragraph> </Section> <Section position="3" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 3.3 Tense predicates </SectionTitle> <Paragraph position="0"> The tense predicates in our logical forrns capture two pieces of information: temporal information and information about action occurrence. This distinction is necessary because actions, whether their time is past, present, or future, need not occur. For example, agents may discuss a future action without ever performing it. Similarly, agents ruay talk about a past action that never occurred, as in &quot;John said that Mary left yesterclay, hut he was wrong&quot;.</Paragraph> <Paragraph position="1"> If thc logical form predicate pasl holds of some action, then that action occurred (in some world or belief context) and its occurrence was in the past. In (7), past is predicated of the action variable x t, denoting the actions described in the main clauses of both (Ta) and (7h). If there is no information to the contrary (e.g., tam utterance is not embedded in an intensional context, established either directly within the utterance, as in &quot;Mary thought she reset the printer&quot;, or through tile discourse context, as when describing a dream), then we call conclude that the action occurred in the real world.</Paragraph> <Paragraph position="2"> Utterances with rationale chmses and mcans clauses differ in what reformation they communicate about the occurrence of the action described in the adjunct clause. In lmithcr construction does this clause involvo a tensed verb, whidl explains why pasl is not predicated of x2 in the LFs of (7a) and (Tb). It is possible, however, to infer from (Ta) that the action denoted by that variable did occur, and from (7b) that it lnight not have occurred, ms illustrated in (1) and (2) m the Introduction. This information is captured by the interpretation rules for means clauses and rationale clauses, as explained in Section 4.</Paragraph> </Section> <Section position="4" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 3.4 Action relations </SectionTitle> <Paragraph position="0"> Finally, the l,Fs in (7) include predicates representing the connectives that link the two clauses in each of the utterances, namely by and in_order_to. The meanlug of these predicates is specified by interpretation rules, presented in the next section, that state necessary conditions on the use of these constructions. It is important to note that these predicates are used only to represent the connectives &quot;by&quot; and &quot;to&quot;introdncing umans clauses and rationale clauses. Other uses of these lexical items are recognizable in a number of ways (e.g., syntactically: &quot;by&quot; followed by a noun phrase, or &quot;to&quot; introducing an infinitival complement (argnment) to a verb, ms in &quot;John wanted to leave&quot;), ~s discussed in Section 5.3; these arc assumed to be represented differently in the I,F.</Paragraph> </Section> </Section> <Section position="7" start_page="0" end_page="0" type="metho"> <SectionTitle> 4 Interpreting action relations </SectionTitle> <Paragraph position="0"> Three relations between actions -- generation, enable mcnt and (~ontrihutes -- that have been motivated independently by research ill plan recognition \[15, 3, 13\] can he employed in tile internretation of utterances AcrEs DE COL1NG-92, NANTES, 23-28 AO~r 1992 2 6 9 PROC, OF COLiNG-92, NANTES, AUG. 23-28. 1992 with means clauses and rationale clauses. In this section we demonstrate this use of these relations, and also provide a definition of enablement.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 4.1 Generation </SectionTitle> <Paragraph position="0"> The generation relation, initially defined by Goldman \[8\], holds of two actions when the performance of the first results in the simultaneous performance of the second. Generation, however, encompasses more than simply two simultaneous actions. For example, Mary can reset the printer by pressing a button only in certain circumstances, namely when the electricity is on, the printer is plugged in, etc. Performing the generating action when these conditions do not hold does not result in the performance of the generated action.</Paragraph> <Paragraph position="1"> Generation, therefore, is a relation that depends upon contextual constraints, called generation-enabling conditions \[15\], that must hold during performance time.</Paragraph> <Paragraph position="2"> This relation was formalized by Pollack \[15\], and subsequently revised in previous work of the author's \[3\]. The following English gloss of the definition suffices for the present discussion and avoids an unnecessary digression into an explanation of the formalization; A and B are actions, comprising an act-type, agent and time.</Paragraph> <Paragraph position="3"> (9) A generates B if and only if 1. A and B are actions performed by the s~me agent at the same time 2. there is a set of conditions, C, such that a. these conditions hold during the performance .time of A and b. the act-type of A conditionally generates the act-type of B under C.</Paragraph> <Paragraph position="4"> Clause (2b) states the requirement that there bc a condilional generation relation between the two act-types and the generation-enabling conditions, C. This relation abstracts away from specific actions to capturc the regularities of a generation relation across occurrences. It holds between act-types ~ and fl and conditions C if (a) whenever an action of type c~ occurs while these conditions hold, an action of type occurs at the same time and (b) neither an occurrence of an action of type a, nor C holding, is by itself sufficient to guarantee the occurrence of an action of type /3 \[15\]. An important property of the generation relation is that if it holds of two actions A and B, and A occurs, then so does B. This follows from the generation relation requiring the relevant conditions to hold during performance time (as stated in clause (2a) in tile definition).</Paragraph> <Paragraph position="5"> In light of the generation relation, we can reconsider the examples in (1). Both these utterances refer to an underlying conditional generation relation: in the right circumstances, pressing the button results in simultaneously resetting the printer. They differ, however, in that they do so from different perspectives: utterance (lb), with the means clause, asserts the occurrence of the generated action (the resetting action), while utterance (la). with the rationale clause. does not (cf. example (2)). Therefore, tbe relevant generation-enabling conditions must have held during performance time in the context of (lb) bug not necessarily in that of (la). Because the generation relation requires these conditions to hold during performance time, it correctly describes the relation between the two actions in (lb) but not necessarily that in (la).</Paragraph> <Paragraph position="6"> Utterances with rationale clauses, like (la), only have the potential for realizing a generation relation, and this potentiality rests on two different factors: (a) the possibility that there is no conditional generation relation between the two actions, as in &quot;Mary ate an apple to reset the printer&quot;, or (b) the possibility that tbe generation-enabling conditions do not hold during performance time, as in (la) where the two actions are related by a conditional generation relation, but the associated generation-enabling conditions might not hold during performance time.</Paragraph> <Paragraph position="7"> The following sections, however, will show that an analysis of rationale clauses based solely in terms of the generation relation is too restrictive.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 4.2 Enablement </SectionTitle> <Paragraph position="0"> The interpretation of rationale clauses also requires appealing to the enablemen~ relation; for example, in (10) below (of. (la)), tile performance of the main clause action does not (potentially) result in the simultaneous performance of the adjunct clause actiou. Rather, it only makes possible the subsequent performance of the adjunct clause action. The generation relation, tberefore, does not correctly describe the action relation in this utterance. Instead, tile relationship is oue of enablement, a relation we define ms holding of two actions when the performance of tile first brings about a condition that is necessary for the subsequent performance of the second \[3\].</Paragraph> <Paragraph position="1"> (10) Mary inserted a diskette to back up her file.</Paragraph> <Paragraph position="2"> Much of the literature that makes use of tile enablement relation has been vague about its intended interpretation, using it at different times to mean different things and not explaining wily one action nmst be performed before the other (e.g., \[18\]). In the following definition, the dependency between the enabling and enabled actions is explained by the role of an intervening conditional generation relation 3. A closer examination of utterance (10), for example, shows that the effect of the enabling action, namely that a diskette be in place, provides the generation-enabling condition of a conditional generation relation between typing somc command and backing up thc associated file.</Paragraph> <Paragraph position="3"> (11) A enables B if and only if 1. the time of A is prior to the time of B, 2. there are a set of conditions, C, and a third action A' such that a. one of the eonditious in C, Ci, holds as a result of the performance of A, and b. the act-type of A' conditionally generates the act-type of B under C.</Paragraph> <Paragraph position="4"> 3This is not the only oossible type of delpendellcv \[3\], AcI~ DE COLING-92, NANTES, 23-28 AOtTtr 1992 2 7 0 PROC. OF COLING-92, NANTES, AUG. 23-28, 1992 If Ci, the condition brought about by the performance of A, is the only element of the set of generation-enabling conditions C, then the performance of A is both necessary and sufficient for the subsequent I)crformance of B.</Paragraph> </Section> <Section position="3" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 4.3 Contributes </SectionTitle> <Paragraph position="0"> So far, utterances with rationale clauses have been interpreted as instances of the generation or enablemcnt relation. This construction, however, can also relate two actions when the chain of relations between them involves both generation and enablement relations, as illustrated in (12a), or a complex action constructor \[3\], as illustrated in (12b): (12) a. Mary built the table to sell it at the market.</Paragraph> <Paragraph position="1"> Mary sold the table at the market to earn money.</Paragraph> <Paragraph position="2"> Mary earned money to pay her rent.</Paragraph> <Paragraph position="3"> Mary built the table to pay her rent.</Paragraph> <Paragraph position="4"> (enablement + generation + enablement) b. l picked up the foot end for us to lift the piano. (simult + generation) Utterances with rationale clauses thus allow for a wide range of relations between the main clause and adjunct clause actions. To capture this phenomenon, we interpret them as iustances of the Contributes relation. This relation, also originally introduced for plan recognition purposes, is defined as the transitive closure of the generation and enablement relations, and the complex action constructors \[13\]. It therefore covers the entire range of relations that can exist between the actions in this type of utterance.</Paragraph> </Section> </Section> <Section position="8" start_page="0" end_page="0" type="metho"> <SectionTitle> 5 Analysis </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.1 Interpretation rules </SectionTitle> <Paragraph position="0"> The inference rules defining the meaning of means clauses and rationale clauses arc given below. Tile by and in_order_to predicates in the left hand side of the rules are the logical form predicates representing the connectives introducing these clauses 4. Tbe verbs &quot;generates&quot; and &quot;contributes&quot; in the right hand side are used here, as elsewhere in tbe paper, in their technical sense, corresponding to the action relations defined in the previous sections. Note that the order of the arguments in the by predicate and generation relation is reversed.</Paragraph> <Paragraph position="1"> (13) a. LFI: by(h,B)-~ B generates A and B occurred.</Paragraph> <Paragraph position="2"> b. LF2: ia_order_to(A,B)---* A contributes to B, within restricted belief contexts.</Paragraph> <Paragraph position="3"> The LF1 rule maps the LF representation of means clause to the generation relation and specifies that the 4This paper does not address the reference problem and assumes that the mapping of action variables in the logical form to action entities in the discourse model has already been aonlied. generating action occurred. This occurrence is a feature of the means clause construction and not of the use of the gerund form to describe the action. Given an utterance with a means clause, it can therefore be inferred that the generated action occurred as a result of the generating one and that the relevant contextual conditions held during performance time.</Paragraph> <Paragraph position="4"> The LF2 rule maps the LF' representation of ratiohale clauses to a Contributes relation within a belief context, capturing the fact that (a) the relation can be any combination of the generation and enablement relations, as well ms the complex action constructors and (b) that the relation between tile two actions is only potential. A new set of action relatious is not needed for representing the potentiality of the action relation in these utterances. Instead, as described in the companion paper \[5\], it is best expressed in terms of the different beliefs and intentions of the speaker (S) and performing agent (G). For example, G could believe a Contributes relation between actions A and B, wlfite S does not; or G and S could both believe the relation, but haw~ different beliefs regarding associated conditions and actions, e.g., G may believe A is necessary and sufficient for B whereas S believes A is only necessary.</Paragraph> <Paragraph position="5"> When utterances with rationale clauses involve silmlltancous actions, then the Contributes relation derived by the LF2 rule specializes to the generation relation. Exactly when such specialization is possible is a plan recognition problem that goes beyond the scope of this paper. Utterances sometimes provide temporal or agency information that can be used to optimize the plan recognition process. In particular, if the performance times, or performing agents, of the two actions are known to bc different, then a specialization to generation is ruled out. When temporal and agency information is not available, then recipes provide anotber source of information for disambiguating rationale clauses \[3, 14\].</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.2 Consequences of the rules </SectionTitle> <Paragraph position="0"> The two interpretation rules LF1 and LF2 predict all of the properties of utterances with rationale clauses and means clauses that were presented in Section 2.</Paragraph> <Paragraph position="1"> Semantic properties: The LF2 rule accounts for the Ambiguity property of rationale clauses by making use of the Contributes relation which can relate either simultaneous or sequential actions. Because the Contributes relation may specialize to a generation relation, the LFI and LF2 two rules account for the Overlap property. Finally, because tile LF2 rule is based on potentiality, while tbe LF1 rule is not, these rnles also account for tile Distinction property.</Paragraph> <Paragraph position="2"> Algebraic properties: It can be shown that the generation and Contributes relations are irreflexive, asymmetric and transitive, rellecting the algebraic properties of the NL utterances that realize them.</Paragraph> <Paragraph position="3"> By describing simultaneous actions performed by the same agent, the generation relation also captures the increased ~rannlaritv of the action description: bv de-AcrEs DE COLING-92, NANTES, 23-28 AOt3T 1992 2 7 1 PROC. OF COLING-92, NANTES, AUo. 23-28, 1992 scribing sequential (as well as simultaneous) actions, the Contributes relation captures the increased distance between the actions described.</Paragraph> <Paragraph position="4"> In addition, these interpretation rules account for the missing agent and time arguments of the actions described in means clauses and rationale clauses. Because the generation relation requires the agents and times of the two actions to be identical, the missing arguments in a means clause can be recovered on the basis of the agent and time information associate'd with the main clause action. The Contributes relation, however, imposes no temporal or agency constraint. Therefore, without additional information, it is not possible to determine whether the agent (when missing) and time of a rationale clause are the same as those of the main clause, el. &quot;I brought this miserable Morgon to enjoy with our dinner&quot; \[2\].</Paragraph> </Section> <Section position="3" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.3 Scope of the analysis </SectionTitle> <Paragraph position="0"> The LF1 and LF2 interpretation rules predict specific facts about English, namely a large set of properties characterizing the differences and similarities between rationale clauses and means clauses. They do so by defining the meanings of the by and in_order_to LF predicates in terms of independently motivated action relations. These predicates are useful for representing not only the meaning of rationale clauses and means clauses, but also that of related constructions. For example, tile in_order_to predicate can be used to represent the connective &quot;so that&quot; in utterances such as &quot;Mary got up early so that she could catch the first train to Montreal&quot;. The by predicate can also be used for non-clausal constructions, as in &quot;John got the information he needed by means of an interview&quot;. Furthermore, these predicates are meant to be language independent. In French, for example, the in_order_to predicate would be used to represent the construction &quot;pour + infinitive&quot;, as in &quot;Marie a regard~ des films pour preparer son voyage au Japon&quot; (Mary watched movies to prepare for her trip to Japan), and the by predicate, to represent the construction &quot;en + gerund&quot;, as m &quot;Marie a pr~par~ son voyage au J upon en regardant des films&quot; (Mary prepared for her trip to Japan by watching movies). Unlike the corresponding English construction, however, the French &quot;en-clause&quot; is ambiguous between a means clause reading (as given in tile English translation) and a temporal reading that can be translated as &quot;while watching movies&quot;. Determining how to disambiguate these two interpretations is an interesting research question.</Paragraph> <Paragraph position="1"> In the remainder of this section, we show how to distinguish algorithmically the constructions to which the LF1 and LF2 rules apply, thereby making it possible for an interpretation system to build the correct LF representations.</Paragraph> <Paragraph position="2"> Rationale clauses: These clauses are optional infinitival adjuncts, introduced either by the infinitival marker &quot;to&quot;, or, when the subject is not missing, by the lexieal item &quot;for&quot; followed by a noun phrase (realizinz the subiect\] followed by &quot;to&quot;. Both these colastructions are optionally preceded by &quot;ill order&quot;. Note that the LF2 rule applies to rationale clauses with or without explicit subjects. For example, given &quot;Mary prepared lobster (in order) for her guests to have a taste of New England cuisine&quot;, Mary's preparing lobster contributes to her guests having a taste of New England cuisine.</Paragraph> <Paragraph position="3"> A large number of to-infinitival clauses (with or without subjects) to which the LF2 rule does not apply can be distinguished on syntactic grounds, namely by not being optional infinitival adjuncts. Utterances that are syntactically ambiguous show a corresponding semantic ambiguity, and the LF2 rule applies to the rationale clause reading; e.g.: &quot;Bush warned his press secretary to prevent a leak&quot;, where tlle infinitival clause may function as an optional adjunct (i.e., realizing a rationale clause) or a complement.</Paragraph> <Paragraph position="4"> Two types of adverbials to which the LF2 rule dees not apply, but which are syntactically indistinguishable from rationale clauses, are comment clauses, as in &quot;John is not sure what to do, to put it brietly&quot;, and outcome clauses, as in &quot;Mary awoke one morning to find the house in an uproar&quot; \[16\]. Given their status as parentheticals, comment clauses are recognizable in text by a comma, and in speecb by intonation (note that without the comma, the infinitival clause becomes a rationale clause). Outcome clauses are restricted to verbs of discovery or to the verbs &quot;be&quot; or &quot;become&quot; (e.g., &quot;She lived to be 10ft'), and are therefore also distinguishable.</Paragraph> <Paragraph position="5"> Finally, there are pnrpose clauses, e.g., &quot;Mary bought a suit to wear at the meeting&quot;. Purpose clauses are also optional infinitival adverbials, but differ from rationale clauses in the mnnber and type of gaps they allow and in their control pattern s \[2, 12\]. They also differ from the superficially similar infinitival relative clauses by not being attached to a noun phrase. Tile LF2 rule, in fact, makes correct predictious for this construction as well, e.g., Mary's buying a suit contributes to her wearing the suit at tile meeting. Purpose clauses with inanimate subjects, however, as in &quot;John bought a shelf to hold his books&quot;, require some adjustment with respect to tbe action's role in the Contributes relation. Actions relations are between actions, and actions are assumed to have human agents.</Paragraph> <Paragraph position="6"> Therefore, ratber tban deriving a Contributes relation between John's buying a shelf and the shelf's holding his books, the system should derive a relation between John's buying a shelf and his having something (namely the shelf) to hold his books. This issue is currently being investigated.</Paragraph> <Paragraph position="7"> Means clauses: These clauses are very easily distinguishable by their form: the lexical item &quot;by&quot; followed by an -lug clanse (in this context, &quot;by&quot; may be treated as a preposition or a subordinator). Apparent counterexamples to the LF1 rule are utterances of the form &quot;Mary pays her rent by building filrniture&quot;, 5Fl'om a descriptive point of view, rationale clauses differ fro~. purpose clauses in that only the former Mlow the paranhrnae with the words &quot;in order to&quot; \[121.</Paragraph> <Paragraph position="8"> AcIXs DE COLING-92, NANTES, 23-28 ^o',rr 1992 2 7 2 PROC. OF COLING-92, NANTES, AUG. 23-28, 1992 in which the two actions are sequential. However, the fact that LF1 does not apparently apply to this example, is a sign that additional pragnmtic reasoning (e.g., conversational implicatures \[9\]) is needed. In this particular example, LF1 does apply, though indirectly through the utterance of which it is a metaphor, namely, &quot;Mary makes a living by building furniture&quot;. The need for further Gricean reasoning of this sort is reflected in the markedness of such examples.</Paragraph> </Section> </Section> class="xml-element"></Paper>