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<?xml version="1.0" standalone="yes"?> <Paper uid="C90-3018"> <Title>GENERATING CONNECTIVES</Title> <Section position="5" start_page="0" end_page="0" type="metho"> <SectionTitle> 4. DISTINCTION BECAUSE/SINCE: POLYPHONIC FEATURES </SectionTitle> <Paragraph position="0"> &quot;Because&quot; and &quot;since ''3 have the same argumen- null tative behavior and give the same fnnctional status to the propositions they connect. Their different usages can be explained using Ducrot's theory of polyphony (Duerot, 1983). Duerot distinguishes between the speaker and the utterers: in an utterance, some segments present beliefs held by the speaker, and others present beliefs reported by the speaker, but attributed to others the ntterers.</Paragraph> <Paragraph position="1"> Using this theory, the difference between &quot;because&quot; and &quot;since&quot; is as follows: in the complex &quot;P since Q,&quot; the segments P and Q can be attributed to different utterers (&quot;since&quot; is polyphonic), whereas in &quot;P because Q,&quot; they must be attributed to the same utterer (&quot;because&quot; is monophonic).</Paragraph> <Paragraph position="2"> Others have described &quot;because&quot; and &quot;since&quot; by noting distributional differences such as: 1. To answer a &quot;why&quot; question, only &quot;beo cause&quot; works: Ai Why did Peter leave? B: Because he had to catch a train.</Paragraph> <Paragraph position="3"> B: *Since he had to catch a train.</Paragraph> <Paragraph position="4"> 2. &quot;Because&quot; has a tendency to follow the main clause while &quot;since&quot; has a tendency to precede it (Quiak et al, 1972, 11.37).</Paragraph> <Paragraph position="5"> 3. &quot;because&quot;-elauses can be the focus of cleft sentences (Quirk et al, 1972): It is because he helped you that I'm prepared to help him.</Paragraph> <Paragraph position="6"> *It is since he helped you that I'm prepared to help him.</Paragraph> <Paragraph position="7"> The given/new distinction gives one interpretation of these differences: &quot;because&quot; introduces new information, whereas &quot;since&quot; introduces given inibrmation (where given is defined as information that the listener already knows or has accessible to him (Halliday, 1985)). Halliday also indicates that, in the umnarked ease, new information is placed towards the end of the clause. And indeed &quot;because&quot; appears towards the end, the nnmarked position of new intbnnation, and &quot;since&quot; towards the beginning. &quot;Because&quot; can be the focus of an It-cleft sentence which is also characteristic of new information (of (Prince, 1978) for example). ' ' Because&quot; can answer a why-question, thus providing new information to the asker. Presenting given information in response could not serve as a direct answer. There are many different types of given information, however (Prince, 1981). Polyphony is one type of given information but it adds an additional parameter: each piece of given information is attributed to a particular utterer. That utterer can be one of the speakers (this is similar to indirect speech), or it can be a mutually known previous discourse. The ability to distinguish how the &quot;since&quot; clause is given (i.e., which utterer contributed iit) is crucial to correct use of sentences like (3). From a father to his child: (3) Since you are so tired, you must sleep.</Paragraph> <Paragraph position="8"> in (3), the speaker presents the hearer as the source of &quot;you are tired,&quot; and uses the fact that the hearer has previously uttered this sentence as the argument for &quot;you must sleep.&quot; If the hearer is not the source of the sentence, this strategy cannot convince him to go to sleep. Given/new in this ease is therefore a polyphonic distinction, and polyphony provides an added dimension to the distinction.</Paragraph> <Paragraph position="9"> In summary, &quot;because&quot; and &quot;since&quot; have the same argumentative and functional status definitions, but they have different polyphonic definitions. &quot;Because&quot; requires P and Q to have the same utterers, while &quot;since&quot; does not.</Paragraph> </Section> <Section position="6" start_page="0" end_page="0" type="metho"> <SectionTitle> 5;. THEMATIZATION PROCEDURE: CUE VS. NON-CUE USAGE </SectionTitle> <Paragraph position="0"> As mentioned in Section 2, the most basic constraint on the use of all connectives, is that the two related propositions say something about the same &quot;thing&quot; (Lakoff, 1971, p. l 18). It must be possible to find a discourse entity that is mentioned in both P and Q for a connection PcQ to be acceptable. We call the set of discom~e entities mentioned in an utterance the theme of a proposition. The constraint is that the themes of P and Q intersect. For example, in (2) &quot;he failed the exam but he is smart,&quot; the entity in common is the person refelTed to by &quot;he&quot; in both P and Q. In simple cases, this common entity can be found among the participants in the process described by the proposition. In many cases, however, the common entity cannot be found in the propositional contents of P and Q, and yet the connection is coherent as shown in (4), (5), and (6).</Paragraph> <Paragraph position="1"> (4) Are you going to the post office? - because I have some letters to send \[i.e., I ask this because ...\] (Quirk et al, 1972, p.752) (5) He paid for the book, because I saw him \[i.e., I claim that because...\] (Quirk et al, 1972, p.559) (6) A: where is she? B: She is sick, since you want to know everything.</Paragraph> <Paragraph position="2"> \[i.e., I talk because you insist...\] (Roulet et al, 1985) We explain these connections by introducing the notion of thematization procedure. The elements of the theme are not limited to the entities mentioned in the propositional content of a proposition. They can also be derived from other aspects of an utterance. In (4) and (5), the theme contains the speech act realized in P: &quot;because&quot; justifies the fact that the locutor asked a question or asserted knowing something, and not the fact asserted or questioned. We say that &quot;because&quot; links on the speech act rather than on the propositional content. The SA thematization procedure adds the feature Speech-Act: to the theme of the proposition Q. In (6), &quot;since&quot; links on the Utterance Act: the fact that B utters &quot;she is sick&quot; is justified by A's insistence on knowing everything (note that &quot;since&quot; does not justify the assertion but the fact that B is speaking at all).</Paragraph> <Paragraph position="3"> It is characteristic of cei~ain connectives to allow ;; Polyphonic mention of a known principle: use since Since turning the switch to the left causes the power to decrease, the transmission capacity decreases.</Paragraph> <Paragraph position="4"> ;; Explanation by a new fact: use because The transmission capacity decreases because you turn the switch to the left. ;; Subordinate act is an imperative - use but Replace the battery, but keep the old battery.</Paragraph> <Paragraph position="5"> ;; Subordinate act can be syntactically subordinate - use although Although you replaced the battery, keep the old battery. Figure6-1: System generated complex clauses linking on certain features or not - that is, to allow the use of a certain thematization procedure. (4) and (5) show that &quot;because&quot; allows the use of the Speech Act thematization procedure and (6) shows that &quot;since&quot; allows the use of the utterance act procedure. We currently use the following thematization procedures in our implementation: Propositional Content, Argumentative Derivation, Functional Status, Speech Act and Utterance Act.</Paragraph> <Paragraph position="6"> In a complete text generation system, the &quot;deep component ''4 given certain information to convey, decides when it is possible to make some of it implicit by using a certain thematization procedure. The effect is to remove certain discoupse entities from the propositional content to be generated. Using a non-PC thematization procedure therefore allows to implicitly discuss certain features of an utterance that may be difficult to address explicitly. The deep module we are currently developing (Elhadad, 1990a) will use politeness constraints (Brown & Levinson, 1987) to decide which thematization is most appropriate.</Paragraph> <Paragraph position="7"> CUE VS. NON-CUE USAGE: Thematization procedures allow us to distinguish cue and non-cue usages of connectives. When a connective links on a feature that is not the propositional content, it does not affect the truth conditions of the propositions, at least in the traditional view. This suggests that non-content linking is in some ways similar to the cue/non-cue distinction discussed in section 2. Our approach does therefore capture this distinction, but with several differences. It describes the structural move performed by the connective (whedler it is a push or a pop, for example) using features of the &quot;nonnal&quot; (i.e., non-cue) interpretation: if C introduces a directive act, it would work as a &quot;pop,&quot; if it introduces a subordinate act, it would be a &quot;push.&quot; Thus, a cue interpretation of a connective differs from non-cue by the thematization procedure; cue usage would be indicated by linking on the functional status, and possibly speech act or utterance act.</Paragraph> <Paragraph position="8"> It remains open whether cue connectives retain all 4Generation systems are generally divided into two modules: a deep module decides what to say and a surface module decides how to say it.</Paragraph> <Paragraph position="9"> other features of non-cue usage: does a connective loose its normal meaning when used as a cue? Some researchers (Grosz & Sidner, 1986, Hirschberg & Litman, 1987) seem to argue that it does: the cue and non-cue usages are actually two distinct words. If that is the case, it would be difficult for a generator to choose among the different cue words that can perform the same structural task. On the other hand, we have no evidence at this point that cue words are not interchangeable (e.g., that &quot;but&quot; is used for one kind of pop and &quot;now&quot; another).</Paragraph> </Section> <Section position="7" start_page="0" end_page="0" type="metho"> <SectionTitle> 6. IMPLEMENTATION </SectionTitle> <Paragraph position="0"> The procedure for selecting connectives is part of FUF, a larger surface generator using the functional unification formalism (Elhadad, 1988, Elhadad, 1990b, McKeown&Elhadad, 1990). Each connective is represented as a functional description capturing the relations between the features of the segments it connects. Functional unification is well suited for our model because constraints on each pragqnatic dimension can be described separately and the formalism handles interaction between these dimensions. The generated sentences in Figure 6-1 typify the kind of sentences our system currently produces.</Paragraph> </Section> class="xml-element"></Paper>