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<?xml version="1.0" standalone="yes"?> <Paper uid="W01-0803"> <Title>Document Structuring a la SDRT</Title> <Section position="3" start_page="0" end_page="0" type="metho"> <SectionTitle> 2 Crash course in SDRT 2.1 Introduction SDRT (Segmented Discourse Representation The- </SectionTitle> <Paragraph position="0"> ory) was introduced in (Asher, 1993) as an extension of DRT (Discourse Representation Theory, (Kamp and Reyle, 1993)) in order to account for specific properties of discourse structure.</Paragraph> <Paragraph position="1"> The original motivation for developing SDRT can be found in Asher's study of the reference to abstract objects in discourse. Asher argues that a sound discourse theory has to cope with some anaphora whose antecedents turn out to be text segments larger than a clause or a sentence.</Paragraph> <Paragraph position="2"> Moreover, it is necessary to reveal a hierarchical discourse structure which makes appear the sites available for anaphora-antecedent binding. Consider the example in (6) taken from (Asher, 1993, p. 318): (6) (1) After 38 months, America is back in space. (2) The shuttle Discovery roared off the pad from Cape Kennedy at 10:38 this morning. (3) The craft and crew performed flawlessly. (4) Later in the day the TDRS shuttle communication satellite was successfully deployed. (5) This has given a much needed boost to NASA morale.</Paragraph> <Paragraph position="3"> The pronoun this (6.5) can only refer to the whole trip or (possibly) to the last mentioned event (TDRS launch). Consequently, the structure of (6) must be such that : i) there exists a constituent which semantically encompasses the whole story (6.1-4), and ii) neither (6.2) nor (6.3) correspond to available constituents for the anaphora resolution when computing the attachment of (6.5) in the context. Avaibility (or openness) of constituents is a formal property that can be accounted for by the use of discourse relations.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 2.2 DRSs as formal discourse units </SectionTitle> <Paragraph position="0"> SDRT can be viewed as a super-layer on DRT whose expressiveness is enhanced by the use of discourse relations. Thus the DRT structures (Discourse Representation Structures or DRS) are handled as basic discourse units in SDRT.</Paragraph> <Paragraph position="1"> Formally, a DRS is a couple of sets a84 U,Cona85 .</Paragraph> <Paragraph position="2"> U (the universe) is the set of discourse referents.</Paragraph> <Paragraph position="3"> Con is a set of conditions which describe the meaning of the discourse in a truth-conditional semantics fashion. For instance, the DRS representing the sentence (7a) is given in (7b).</Paragraph> <Paragraph position="5"> Note that in addition to individual referents (a11 ), U includes event referents (a1 ). DRT adopts a Davidsonian approach (Davidson, 1967): it considers that events have to be denoted by singular terms in the logical form of sentences. In the semantic model, events are handled as world immanent entities, and event referents (a1 ) can occur in argumental slots of certain predicates (like fcausea15a17a1a46 a5a7a1a27a8a27a19 in (3b)). The statement a1 -leavea15a18a11a62a19 is a predicative notational variant and stands for &quot;a1 is a leaving ofa11 &quot;.</Paragraph> <Paragraph position="6"> DRSs do not correspond to linguistic categories but are formal units: from the SDRT point of view, one should see them as (intensional) meaning structures. This is why some discourse abstract objects (such as facts, situations, propositions...) can be referred to by discourse referents (we will say that they are reified) and semantically characterized by (sub-)DRS. (8) is an example of a fact reading, where a87 is the characterization predicate (Asher, 1993, p. 145).</Paragraph> <Paragraph position="7"> (8) a. The fact that Fred left abruptly upset</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 2.3 Discourse Relations and SDRSs </SectionTitle> <Paragraph position="0"> A SDRS is a couple of sets a84 U,Cona85 . U is a set of labels of DRS or SDRS which may be viewed as &quot;speech act discourse referents&quot; (Asher and Lascarides, 1998). Con is a set of conditions on labels of the form:</Paragraph> <Paragraph position="2"> a discourse relation (structuring).</Paragraph> <Paragraph position="3"> The set of SDRT relations includes Narration (for temporal sequence), Background (for temporal overlap), Elaboration (for whole-part or topicdevelopment), Explanation and Result (for causation), Commentary (for gloss).</Paragraph> <Paragraph position="4"> According to (Asher, 1993, p. 319), (9) sketches the SDR-theoretic analysis of (6) where eacha82a4a95 stands for the DRS representing the content of the a97 th sentence in (6).</Paragraph> <Paragraph position="6"> SDRSs are built by means of non monotonic rules that encodes discourse properties and world knowledge. For instance, one rule states that if a discourse constituent a101 may be connected to a discourse constituent a102 in the context, then normally the relation Narrationa15a102 a5a101 a19 holds. Another rule states that ifa101 may be connected to a102 and if the main event of a101 , i.e. mea15a101 a19 , is known as a cause of mea15a102 a19 , then normally the relation Explanationa15a102 a5a101 a19 holds.</Paragraph> </Section> </Section> <Section position="4" start_page="0" end_page="0" type="metho"> <SectionTitle> 3 Comparison with RST </SectionTitle> <Paragraph position="0"> As nearly everybody in the NLG community uses RST (Rhetorical Structure Theory, (Mann and Thompson, 1987)) as a discourse framework, it is generally considered that the task of document structuring is to produce a tree in the RST style.</Paragraph> <Paragraph position="1"> Since RST is a descriptive theory without any formal background, there exists a wide range of interpretations and several notions of Rhetorical Structure. For some authors, e.g. (Marcu et al., 2000), the Rhetorical Structure is very surfacic: it is an ordered tree isomorphic to the linearized structure of the text and a rhetorical relation can be viewed as a nickname for a small set of cue phrases. For other authors, the rhetorical structure is more abstract: it aims at representing meaning.</Paragraph> <Paragraph position="2"> For example, in (RAGS Project, 1999; Bouayad-Agha et al., 2000), the Rhetorical Structure is an unordered tree in which terminal nodes represent elementary propositions, while non terminal nodes represent rhetorical relations which are abstract relations such as cause. This rhetorical representation is mapped into a Document Representation which is an ordered tree reflecting the surfacic structure of the text.</Paragraph> <Paragraph position="3"> Our approach is closer to the RAGS'one if we consider our logical form as equivalent to their Rhetorical Structures. However, we differ basically on the following point: their Rhetorical Structure is a tree, while our logical form, when graphically represented, is a (connex) graph and not a tree. Let us justify our position by considering the discourses in (10).</Paragraph> <Paragraph position="4"> (10) a. Fred run the vacuum cleanera103 while Sue was sleepinga104 in order to bother hera105 .</Paragraph> <Paragraph position="5"> b. Fred run the vacuum cleanera103 while Sue was sleepinga104 in order to please hera105 .</Paragraph> <Paragraph position="6"> They can be given various meanings, however we focus on the following: a78 for (10a), running the vacuum cleaner is supposed to be noisy and Fred attempts to bother Sue by making something noisy exactly when she is sleeping, a78 for (10b), running the vacuum cleaner is supposed to be an awful chore and Fred attempts to please Sue by relieving her of a chore. It just happens that he run the vacuum cleaner while she was sleeping.</Paragraph> <Paragraph position="7"> In RST, both (10a) and (10b) are given the tree representation in (11), in which CIRC abbreviates</Paragraph> <Paragraph position="9"> The semantic interpretation of a rhetorical tree is given by the &quot;nuclearity principle&quot; (Marcu, 1996): whenever two large spans are connected through a rhetorical relation, that rhetorical relation holds also between the most important parts of the constituent spans. In (11), the nuclearity principle amounts to saying that there is only one interpretation, namely that in which the nucleus argument of PURPOSE is a109 , which is the nucleus argument of CIRCUMSTANCE. This is the right interpretation for (10b). However, (11) cannot represent the meaning of (10a) for which the first (nucleus) argument of PURPOSE is the sub-tree rooted at CIRCUMSTANCE. In conclusion, a RST tree structure is too poor: it cannot account for the expressiveness of texts. This can be accounted for by the use of representations which correspond graphically to (connex) graphs. The graphical representations of (10a) and (10b) and their equivalent in pseudo logical forms are respectively shown in (12a) and (12b)5.</Paragraph> <Paragraph position="10"> STANCE. It is the interpretation of the RST tree in (11) without the nuclearity principle. (12b) is a graph in whicha109 is part of two relations6. This graph corresponds to the interpretation of the RST tree in (11) given by the nuclearity principle. This principle makes that a109 is part of both the relation PURPOSE with a121 and the relation CIRCUMSTANCE with its satellitea115 .</Paragraph> <Paragraph position="11"> The SDRSs underlying (10a) and (10b) are shown respectively in (13a) and (13b) (the notation a94a64a103 stands for the DRS representing a109 and so on). Here we replace CIRCUMSTANCE by the SDRT relation Background for temporal overlap7.</Paragraph> <Paragraph position="12"> 5The arguments of a binary semantic predicate are noted as 1 and 2 after the fashion of MTT (Meaning to Text Theory, 7Actually, the SDR-theoretical representations of (13) should be more complex with a pseudo-topic that would s-</Paragraph> <Paragraph position="14"> In (13a), the first argument of Purpose is a42 which groups a94 a103 and a94 a104 which are linked through Background. In (13b), a42 a3 is part of two discourse relations. The graphical representations of (13a) and (13b) (in which Ra15a42 a3a134a5a42 a8a27a19 is represented as a tree rooted at R) have the same topology as (12a) and (12b) respectively.</Paragraph> <Paragraph position="15"> In summary, in document structuring approaches based on RST, a rhetorical structure is always a tree, whenever understood as abstract representation or a more surfacic one. This cannot be maintained. First, if the rhetorical structure is an abstract conceptual representation closed to a logical form, its graphical representation is a connex graph (and not always a tree). Second, if the rhetorical structure is a discourse representation, as it is the case for SDRS, its graphical representation is also a connex graph.</Paragraph> <Paragraph position="16"> This criticism is not the only one against RST.</Paragraph> <Paragraph position="17"> This discourse framework has already been criticized in the generation community (de Smedt et al., 1996). So we advocate the use of SDRT. This theory presents the following advantages : a78 it is a formalized theory which benefits of all the progress in formal semantics most often realized in the understanding perspective around DRT or SDRT.</Paragraph> <Paragraph position="18"> a78 adopting SDRT for text generation by &quot;reversing&quot; the rules (see (4) reversed in (5)) allows us to have reversible systems: the same linguistic data can be used for both text understanding and generation.</Paragraph> <Paragraph position="19"> a78 as it will be shown in section 5, the document structuring component a la SDRT gives hint on referring expressions: it indicates when a pan the Background-related constituents. See (Asher and Lascarides, 1998) for details.</Paragraph> <Paragraph position="20"> discourse referent should be expressed as an anaphoric NP.</Paragraph> <Paragraph position="21"> a78 a SDRS (i.e. a document plan) can be given to existing microplanners and surface realizers with perhaps some modifications (see section 6). For example, a SDRS can be given as input to G-TAG (Danlos, 2000) implemented in CLEF (Meunier and Reyes, 1999) provided small fits are realized.</Paragraph> <Paragraph position="22"> In conclusion, we think that SDRT is a better discourse framework than RST (for both text generation and understanding).</Paragraph> </Section> <Section position="5" start_page="0" end_page="0" type="metho"> <SectionTitle> 4 Equivalence between logical forms </SectionTitle> <Paragraph position="0"> Recall that we want to compute both the SDRS in (3a) with Result and the SDRS in (3b) with Commentary from the logical form in (1). Let us show that the logical forms derived from these SDRSs are equivalent. In SDRT, there is an axiom for Result from which one can entail the rule in (14), which is similar to the axiom in (4) for Narration.</Paragraph> <Paragraph position="1"> (14) Resulta15a42 a3a9a5a42 a8a9a19a81a80 causea15a18a138a139a1a44a15a42 a3a45a19a86a5a12a138a139a1a44a15a42 a8a43a19a12a19 Therefore, the logical form derived from (3a) The difference between (15) and (16) consists in considering the causal relation between the two events either as only a predicate or as a variable plus a predicate. However, the axioms in (17a) and (17b) can be laid down. With these axioms, (15) and (16) are equivalent since they are both equivalent to (18), in which the causal relation gets represented twice. In other words, we have the following logical entailments: (15), (17a) a142 (18),</Paragraph> <Paragraph position="3"> Let us underline that the content determination task may arbitrarily result in (15), (16) or even (18). Therefore, the document structuring task has to produce SDRS such as (3a) and (3b) from one of these logical forms.</Paragraph> <Paragraph position="4"> There is a an important difference between SDRSs and logical forms. SDRSs represent discourses and their variables are discourse referents. Logical forms represent meanings and their variables are pure logical variables. To compute a SDRS from a logical form, one has to decide which variables from the logical form become discourse referents, as explained in the next section. null</Paragraph> </Section> <Section position="6" start_page="0" end_page="0" type="metho"> <SectionTitle> 5 Building SDRSs </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.1 Basic principles </SectionTitle> <Paragraph position="0"> To get a recursive process, first, we translate the logical form into a DRS8. In case of a purely existential formula such as those we have been dealing with so far, this just amounts to putting all the variables into the universe of the DRS and split the formula into elementary conjoined conditions9. The document structuring task amounts then in building a SDRS from a DRS. The simplest way to do that is simply to transform : course relation a155 a3 to be established between a42 a3 and a42 a8 must have conditiona46 among its consequences: no other element is in charge of expressing conditiona46 .</Paragraph> <Paragraph position="1"> In SDRT for text understanding, the conditions are not ordered. However, in text generation, a document plan indicates the order of its components. As a consequence, when a document plan is a SDRS, its components (labelleda42a24a95 ) have to be ordered. In the pseudo SDRS above, it is supposed thata42 a3 precedesa42 a8 which precedesa42 a46 .</Paragraph> <Paragraph position="2"> Let us examine the principles governing the splitting of the conditions and the universes. For the splitting of the conditions, the whole content of the factual database has to be verbalized. Therefore all the conditions in the DRS have to be expressed in the SDRS. Two cases appear: a78 either a condition in the DRS appears as a condition in one of the sub-DRS; that is the case fora157a37a43a35a38a158 a97a129a159a77a97a37a26a35 a3 in the DRS labelleda42 a3 ; a78 or it is expressed through a discourse relation; that is the case for a157a37a26a35a38a158 a97a127a159a132a97a37a26a35 a46 . One of the criteria for choosing an appropriate discourse relation is that its consequences have to contain the condition involved. For example, the condition causea15a17a1a10a3a9a5a7a1a9a8a27a19 can be expressed through Resulta15a42 a3a9a5a42 a8a27a19 whena42 a3 and a8 label the sub-DRSs that contain the descriptions ofa1a10a3 anda1a9a8 respectively.</Paragraph> <Paragraph position="3"> Let us now look on how to determine the universes of the sub-DRSs, i.e. the discourse referents. First, there are technical constraints, namely: null a78 the arguments of any condition in a sub-DRS must appear in the universe of this DRS; a78 the universes of all the sub-DRSs have to be disjoint. This constraint is the counterpart of the following constraint in understanding: &quot;partial DRSs introduce new discourse referents&quot; (Asher, 1993, p. 71).</Paragraph> <Paragraph position="4"> These two constraints are not independent. Assuming that the first constraint is respected, the second one can be respected with the following mechanism: if a variable a11 already appears in a preceding sub-DRS labelled a42a24a160 , then a brand new variablea14 is created in the universe of the current sub-DRS labelled a42a24a161 and the condition a14a162a29a163a11 is added into the conditions of a42a69a161 . The discourse referent a14 will be generated as an anaphora if a42a24a160 is available to a42a69a161 (see section 2.1), otherwise it will be generated as a definite or demonstrative NP.</Paragraph> <Paragraph position="5"> Secondly, as mentioned in section 4, it has to be decided which variables become discourse referents. When we have for instance a0 fa5a7a1 a3a5a7a1a8 f-causea15a17a1 a3a5a7a1a8 a19 , we can decide to apply axiom (17b), and then remove the variable f and every condition having f as an argument (in particular the condition f-causea15a17a1a10a3a9a5a7a1a27a8a27a19 ). In order for such an operation to be valid, we have to ensure that no information is lost. In practice, this supposes that no other condition than f-causea15a17a1a4a3a9a5a7a1a9a8a27a19 has f as an argument. We call this operation dereification. Conversely from such a formula as a0a146a1a4a3a6a5a7a1a9a8 causea15a17a1a10a3a43a5a7a1a9a8a27a19 , we can apply axiom (17a), and then remove the condition causea15a17a1a4a3a9a5a7a1a9a8a27a19 . We call this operation reification. Contrarily to dereification, no information can be lost. These two operation are a mix between something which is pure logic (that adds information) and a discourse operation that deals with discourse referents. As our objective is to build as much dicourse plans as possible, reification and de-reification are systematically performed whenever possible.</Paragraph> <Paragraph position="6"> The process is recursive: once all this is done (splitting the conditions, universes determination (including reification and de-reification) and choice of discourse relations), the process can apply recursively on each of the embedded DRSs (this is the reason why the logical form is first translated into a DRS).</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.2 Algorithm </SectionTitle> <Paragraph position="0"> A naive solution to implement these principles will be first described. Next some refinements will be proposed.</Paragraph> <Paragraph position="1"> The naive solution amounts to considering all the possible splittings of the set of conditions. If there are a35 conditions, the number of sub-SDRSs ranks from a113 toa35 . In the hypothesis of a splitting into a164 sub-SDRSs, each condition may be put in any of thea164 sub-SDRSs or in any of thea164a166a165 a113 sets of conditions to be expressed by a discourse relation10. Next the universes of the sub-SDRSs are built according to the principles described above.</Paragraph> <Paragraph position="2"> This leads to availability constraints (e.g. a42a69a160 is available toa42a69a161 ) to be checked later on. In the next step, the possible discourse relations are computed according to their consequences. At this step, a lot of hypotheses are ruled out. For example, any hypothesis assuming that a condition such as a1 -leavea15a18a11a71a5a12a14a146a19 is to be expressed through a discourse relation will be ruled out. Finally, the availability constraints have to be checked using the same rules as in understanding.</Paragraph> <Paragraph position="3"> With this naive solution, a lot of document plans will be rejected by the linguistic component. As an illustration, each sub-SDRS has to be verbalized as a clause (see section 6). Therefore, any sub-SDRS that does not include an eventuality or a fact will be rejected by the linguistic component. null This naive solution is theoretically valid, however it is not usable in practice. A lot of possible failures can be foreseen. For example, the conditions that can be expressed through a discourse relation, e.g. causea15a17a1 a3a5a7a1 a8 a19 , should be considered first. If it is decided that such a condition is indeed expressed by a discourse relation, e.g. Resulta15a42 a3a27a5a42 a8a6a19 , then the sub-SDRSs a42 a3 and a42 a8 are created with the conditions concerning a1a4a3 and a1a27a8 respectively.</Paragraph> <Paragraph position="4"> To sum up, the process of splitting the conditions should not be blind. The content of the conditions has to be taken into account in order to guide the splitting and avoid thereby failures that can be foreseen. However, the details of this optimization will not be presented here.</Paragraph> <Paragraph position="5"> 10In SDRT, any element in the universe of a SDRS must be linked to another element. Therefore, a SDRS witha167 sub-SDRSs must include (at least)a167 a151a140a168 discourse relations. 6 Generating a text from a SDRS A SDRS, i.e. a document plan, is given to a micro-planner and surface realizer which computes one or several texts. It is the topic of another paper to explain in detail this process. Here we will only give the basic principles which guide the choices to be made in the tactical component.</Paragraph> <Paragraph position="6"> The process to generate a text from a SDRS a84 U,Cona85 is basically recursive: a78 an element a42a69a95 in U has to be generated as a clause if a42 a95 labels a DRS and recursively as a text (possibly a complex sentence) if a42a69a95 labels a SDRS.</Paragraph> <Paragraph position="7"> a42a93a92a57a94 in Con where a94 is a DRS a84 U,Cona85 has to generated as a clause according to the following constraints: - in analysis, a discourse referent is the trace of either a determiner or an inflexion mark. Therefore, in generation, a discourse referent has to be generated as an NP or a tensed verb (noted V). Such an information is noted as e.g.</Paragraph> <Paragraph position="8"> a1 a3 :NP/V; - the conditions guide the lexical choices. The conditions a11a173a29 Fred correspond to proper names which is noted asa11 :PN[Fred]. The equality conditions between discourse referents (e.g. a11a174a29 a14 ) give rise to (pronominal or nominal) anaphora which is noted as a11 :ANA[a14 ].</Paragraph> <Paragraph position="9"> The other conditions are associated to lexical predicates.</Paragraph> <Paragraph position="10"> With these constraints, an element which is reified, e.g. f-causea15a17a1a10a3a9a5a7a1a27a8a27a19 , gives rise to an NP or a verb (a cause of, provoke) and an element which is not reified, e.g. causea15a17a1a10a3a9a5a7a1a27a8a27a19 , gives rise to a modifier on a1 a3 or a1 a8 with a1 a3 anda1a27a8 generated either as verbs or NPs.</Paragraph> <Paragraph position="11"> This process results in a list such as: Such a list guides the lexical choices and syntactic realization performed by the micro-planner.</Paragraph> <Paragraph position="12"> 7 Illustration on examples Let us show how to compute the SDRSs in (3a) and (3b) from the logical form in (1). First, this formula is translated in the DRS in (19), in which the conditions are numbered for the sake of convenience. null</Paragraph> <Paragraph position="14"> From (19), one possibility is to express conda46 through Resulta15a42 a3a9a5a42 a8a9a19 in which a42 a3 and a42 a8 label the sub-DRSs grouping the conditions on a1a10a3 and a1a9a8 respectively. Therefore, a42 a3 has to group conda3 and conda176 . As conda3 introduces the variable a11 , conda177 has to figure also in a42 a3 11. The universe of the DRS labelled by a42 a3 is a178 a1a4a3a9a5a12a11a38a179 . Similarly for a42 a8 , its universe is a178 a1a9a8a10a5a12a14a180a179 , its conditions are conda8 , conda181 and conda182 . All the conditions of (19) are therefore expressed in (3a) which is a well-formed document plan. Following the rules sketched in section 6, (3a) will be generated in (2a) by the linguistic component, if Result is lexicalized as the cue phrase therefore which links two sentences.</Paragraph> <Paragraph position="15"> From (19), another possibility is to split all the conditions into two sub-DRSs: the first one labelleda42 null a3 grouping the conditions ona1a4a3 (as in the previous possibility), the second one labelled a42 a8 grouping all the other conditions. conda46 ina42 a8 has a1a10a3 as argument. This variable already appears in a42 a3 . Therefore a brand new variable a1a46 is created in the universe of a42 a8 and the condition a1 a46 a29a183a1a4a3 11This is an optimization: if cond a100 were not included in a49a51a50 , the surface realizer would fail ona49a51a50 and the hypothesis would be ruled out.</Paragraph> <Paragraph position="16"> is added ina42 a8 . As all the conditions are split into the sub-DRSs, a42 a3 and a42 a8 have to be linked with a discourse relation which adds no information (i.e. which has no consequence). Commentary is such a discourse relation, and it is valid here since its constraint (one element ina42 a8 has to be coreferent with one element in a42 a3 , see section 1) is respected with the coreference relation a1 a46 a29a184a1a4a3 . At this step, the SDRS in (20) has been built.</Paragraph> <Paragraph position="17"> From (20), one possibility is to transmit this SDRS as it is to the tactical component. If Commentary is lexicalized as an empty cue phrase linking two sentences, (20) will be generated in (21) where causea15a17a1a46 a5a7a1a27a8a27a19 , which is not reified, is expressed through the modifier because of.</Paragraph> <Paragraph position="18"> cause of that.</Paragraph> <Paragraph position="19"> In text understanding, (21) is likely to be analyzed with the discourse relation Narrationa15a42 a3a9a5a42 a8a27a19 , which has for consequence a1a4a3 a33 a1a27a8 . This condition is compatible with those in a42 a8 since causea15a17a1 a46 a5a7a1a9a8a27a19 with a1a46 a29a186a1a4a3 implies a1 a3a187a33 a1 a8 . So, there is no conflict between the understanding and the generation of (21).</Paragraph> <Paragraph position="20"> From (20), another possibility is to reify causea15a17a1a9a46a10a5a7a1a8 a19 in a42 a8 . The SDRS in (20) becomes that in (3b). If f-cause is lexicalized as bring into (a colloquial variant of cause when the second argument is a fit of tears), (2c) will be generated.</Paragraph> </Section> </Section> class="xml-element"></Paper>