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<?xml version="1.0" standalone="yes"?> <Paper uid="C94-1060"> <Title>ON LEXICALLY BIASED DISCOURSE ORGANIZATION IN TEXT GENERATION</Title> <Section position="1" start_page="0" end_page="0" type="metho"> <SectionTitle> ON LEXICALLY BIASED DISCOURSE ORGANIZATION IN TEXT GENERATION </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> Summary </SectionTitle> <Paragraph position="0"> In this paper, we show that Reileralion and Collocation relations as introduced I)y Ilalliday and llasan may function as lexieally I)iased discourse structure relations and that these relations are well represented by sequences of Mel'&flds Lexical Funclions (Ll,'s). We propose to use Lie sequences for tl,e final determination and realization of discourse organization during lexical choice in text generation.</Paragraph> </Section> </Section> <Section position="2" start_page="0" end_page="0" type="metho"> <SectionTitle> 1 LEXICAL PHENOMENA IN DIS- COURSE </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 1.1 The Problem </SectionTitle> <Paragraph position="0"> In text generation, the tmsk of content selection and discourse organization, i.e. text phuming, has often been opposed to the task of linguistic realization ()1&quot; the information selected and organized by the text planning process (el., e.g., MeKeown and Swartout, 1987).</Paragraph> <Paragraph position="1"> However, discourse organization is not possibh', without taking into account linguistic means that are available to express a particular meaning (el., e.g., Meteer, 1992; Rubinoff, 1992). Esl)e.eially the \['allure to integrate lexical choice into the phuming process may lead to monotonous, awkward, or even ungrammatical text (note that when used separately, the clauses in (Ix) and (2a) are fully acceptable):' (I) a. ? Alle bewahrten Ruhe; nut llans holtrite keine lbtlw/(sie nieht) \]~ew~bE,Lt! lit. 'All kept cabnness; only l\[ans could not keep c,~hnness/ it'.</Paragraph> <Paragraph position="2"> VS.</Paragraph> <Paragraph position="3"> b. Alle bewahrten Ruhe; nnr llans konnte nicht rnhiq blciben lit. 'All kept calmness; only I lans eouhl not kee l) cahn'.</Paragraph> <Paragraph position="4"> (2) a. ? l)er langgephmte AusJlu9 fired a,n Sonntag start; wir unternahmen ihn mit der 9anze;, 1'braille lit. 'The long-pl~tnned trip took platte on Sunday; we undertook it with the entire family'.</Paragraph> <Paragraph position="5"> VS.</Paragraph> <Paragraph position="6"> b. Der hmggephmte Attsfln 9 fand ant Sonntag stalt; die (mnze l'hrnilie nahm daran teil lit. 'The iong-phuumd trip took pl~tcc on Sunday; the entire family took part in it'.</Paragraph> <Paragraph position="7"> 1 In the following exatnples~ the inal)prol)viate lexieal expression in the (a) sentences and its IllOl'e alq)rol)riatc alternat, ive in the (b) sentences are underlined.</Paragraph> <Paragraph position="8"> (3) a, *lhtns muel, te clue Entdeckun9; diese Entdccktmg war wirklich lit. 'll;uts m~ule ~ discovery; this discovery was real'.</Paragraph> <Paragraph position="9"> VS.</Paragraph> <Paragraph position="10"> b. llans maehte eine lrnldeckun.q; diese lCntdeekun9 war eine I')ntdeekung i m wahrslen PS'inne des I'Vorles lit,. 'Ilans made ~ discovery; this discovery was a discovery ill the real SellSe of the word'. These examples show thai, lexicaI constraints are of a sl)e('ial relewmee to discourse org;mization if related discourse segments conmmnicate illfOrlll&tiOll on lilt(! same or related object, event, process, etc. While in the past, considerable work has been done on the realization of anaphoric links between related entities via referring expressions (ef., e.g., Tutin and Kittredge, 1092; Dale, 1980; Relier, 1091), only a few pro\[)osals eml)hasize the relewmee of lexical means for the realization o1&quot; discourse struel:nre relations such ;m CON-TItAST in (11)) and ELABORA'PION ill (2t)) and (3b), 2 It is iml>ori.ant to note that the actual realization of a discourse relation mw vary with the semantics of the lexemes involved. For examl)le , ill (4), the second ebmse is an IN'I'I,HU'II.I,~TATION or CONSI,IQUENCE of the lit'st; despite the analogous syntactic construction in (5), tim second clause is a JUSTIFI(:ATION or an EXPLA-NATION of the first rather than an tNTI,',It.I'RETATION or CONSEQU\[,INCI ,l .</Paragraph> <Paragraph position="11"> (4) l/e t,'avels ,, lot he is a '1,,'ofeasional' traveller.</Paragraph> <Paragraph position="12"> (5) Ile jlics a lot - he is a professional Jlier.</Paragraph> </Section> </Section> <Section position="3" start_page="0" end_page="0" type="metho"> <SectionTitle> 11.2 The Proposal </SectionTitle> <Paragraph position="0"> .quch relations as those between Ruhe bcwahren '\[to\] kee l) eahnness' and ruhi9 bleiben '\[to\] keep cMm' (ill 1); between Ausfl'ng finde! slall 'trip t~tkcs place' and am Ausflug leilnehmen '\[to\] take part in the trip' (in 2); and bet, ween eine Enldeckung 'discovery' and im wahrslen Sinne des Worles % the real sense of the word' (in 3) have been introduced by (l\[alliday and Ilasan, 1976) as Reiteration and Collocalion relations, a 21n this paper, we use the \]llllll{!S of diSCollrse S~,l'lletitlrC/! tel;tlions as they are known from the Rhetorical Sh'uclttre 7'heovy (Mann and Thompson, 1987').</Paragraph> <Paragraph position="1"> 3All.hough preferably used so flu' to describe dlscom'se links hetween infiwmatiol~ segments realized by norms, Reiteration and Collocation relations may well hohl between segments which m'e realized by other parts of speech and evell })y multiple word 12xl)ressi()lIS, Reiteration stands for a strict repetition on a lexieal expression in related discourse segments; for a substitution of a lexical expression by a synonym, or for a substitution by a snperordinate. Consider the following examples, which illustrate the three different reiteration relations (strict repetition in (7a), synonymy in (7b), and superordination in (7c)): (6) Last summer, Monica flew to Italy, (7) a. while Daniela flew to Norway.</Paragraph> <Paragraph position="2"> b. while Daniela took the plane to Norway. null c. while Daniela travelled to Norway.</Paragraph> <Paragraph position="3"> Further substitution relations such as metaphoric repetition (7d), negated az~tonyray (7e), etc. can be added: (7) d. while Daniela wafted away to Norway.</Paragraph> <Paragraph position="4"> e. Daniela also did not stay at home.</Paragraph> <Paragraph position="5"> Collocation stands for 'any recognizable lezicosemastic relation' between lexicM expressions in related discourse segments. Examples of collocation relations are attribution (7f), partition (7g), means (7h), etc.: (7) f. it was a very pleasant journey.</Paragraph> <Paragraph position="6"> g. making a stop over in Munich.</Paragraph> <Paragraph position="7"> It. it was one of those ~ifl aircrafts.</Paragraph> <Paragraph position="8"> As our examples show, reiteration and collocation relations help to ensure not only cohesion, but also coherence in texts. Therefore, a text generator has to provide an organization of lexical resources that tailors discourse structure relations to reiteration and collocation relations. This presupposes, on the one hand, a precise picture of which reiteration and collocation relations are available in language and how they are realizable; and, on the other hand, a fine-grained discourse model that contains these relations.</Paragraph> <Paragraph position="9"> To make allowance for the global discourse organization, which is performed independently from lexical resources, we suggest a two level text planning task implementation, with the first level realized by a Rhetorical Struclure 7'heory (its'r) (M ann and Thompson, 1987) style text planner and the second level -by a separate lexical choice module. Then, the discourse organization of a text is done in two steps: in the first step, the text planner predetermines the discourse structure relations; in the second step, the lexical choice module provides, in accordance with linguistic constraints, the final determination and the realization of these discourse structure relations.</Paragraph> <Paragraph position="10"> The present paper reports an attempt to define lexieally biased discourse structure relations used in a partially implemented lexical choice module. I)ue to the lack of space, we do not discuss the module itself; it is described in detail in (Wanner, 1992, 1994). Here, we demonstrate how discourse organization for text generation can be refined by lexically biased discourse structure relations and how these relations are related to global discourse relations specified in the output of an RST style text planner.</Paragraph> <Paragraph position="11"> In contrast to the most discourse models (cf., e.g., McKeown, 1985; Ch'osz and Sidner, 1986; Mann and Thompson, 1987), which take the clause ~ts the minimal discourse segment, we consider as discourse segments &quot;perspectives&quot; (cf. McCoy, 1989)- specific views taken on a semantic entity (an object, an ew~'nt, etc.). A perspective is a wording which is tailored to the lexical repertoire of an entity; it is realizable as a clause, a phrase, or as a single lexeme. Each of the clauses in the examples above can be considered as a realization of a single perspective; ~md the reiteration and collocation relations that hold between the clauses as well-defined perspective pairs.</Paragraph> <Paragraph position="12"> In our model, a single perspective is represented as a composition of Mel'&fl~'s Lexical l,~unctions (hereafter LFs) (Mel'&fl{ and Polgu~re, 11987); perspective pairs are represented as LI~' sequences.</Paragraph> <Paragraph position="13"> The lbllowing distinctive features characterize our model: * it makes snre that all relations defined ~tre expressible in language, * it allows for a realization of lexicM relations as subclansal relations between discourse segments, * it is sensitive to lexical and syntactic wtriations \['or the realization of discourse structure relations.</Paragraph> </Section> <Section position="4" start_page="0" end_page="371" type="metho"> <SectionTitle> 2 LEXICAL FUNCTIONS IN DIS- COURSE </SectionTitle> <Paragraph position="0"/> <Section position="1" start_page="0" end_page="370" type="sub_section"> <SectionTitle> 2.1 The Basics </SectionTitle> <Paragraph position="0"> Formally speaking, an L~ f is a standard semanticolexical relation which holds between a lexeme 1,1 (the keyword of f ) and a set of lexemes f(t,) (the wdue of f). Examples on LFs are:</Paragraph> <Paragraph position="2"> = \[to\] put to sleep Manif( happy) : \[to\] beam with joy Mel'&lk distinguishes about sixty simple t,l,'s on the above Idnd. Simple LI,'s can further be combined with strict repetition (l/o\] ha,w a look A \[lot have a look) synonymy (\[t,,\] di.wJp,~o,&quot; A \[&quot;4 v,,r,m,) superordination (l/o\] searclt (a Jtal) A reprisal) metaph, rel)etition (\]o:1A ,..H '4 \]+::J) neg. atttonymy (close A not far away) conversion (I/o\] sell A \[lot I, uy) process-actor (\[to\] lie A li.,') cause-pFocess (\[lot v,,l lo .~l,..j, A\[M .+t,,.p) init ializat ion-process (\[to\] fldl ash:ep A \[to\] .~leep attribution ( beaulifld A real beattlg) manifestation (\[lot bc happy A \[1o\] be,,m ,,:ill, jog) 'Pabh'. 1: q'he realization o1&quot; reil.eration and collocation relations by LI,' sequences each other; l.he meaning of such comphs: LFS is, as a rule, a eombitmtion of the meanings of tim participating l.Fs. q'hus, Ant.iMagn lneans 'slightly' (e.g., AntiMagn(i,0ury ) = minor); and Incel)()lmrl 'start performing' (e.g., htcepOpert( delmle) = \[lot shirt (a debate)). 4 In text generation, the bettellts from l.t.'s are I, hreefold: (i) they provide subclausal collocational constraints l)etween the keywor<ls aiid the wdues (<:f. h:r: danskaja el al., 199 l) as, e.g., between narrow and majo,'ity (with AntiMagn(majoritv) = narrot,) i,, Ilo,,dini won with a narrow majority; (ii) they provide interclausal cooccurrenee links (el. 'l'utin and Kittredge, 1992) between the keywords and ,,he wdues as, e.g., between spaghetti and pasla (with Gener(spaghetli) = pasla) in Let's take spaghetti; pasta is not bad he.re; and (iii) they allow \['or explMt statement:s on tit('+ coo('eurfence between values orw~rious LFs ill relal;ed discourse segments, as, e.g., between the values of Vil(sler'p) \[to\] sleep at,d h, cep(steep) -- \[to\] si,k i,lo sl,,ep i,t llardly in bed, 7bny sank into sleep and slept all the night till the morning.</Paragraph> <Paragraph position="3"> In our work, we use (i) for single perslmet.ive reatizal.ions (ef. Wanner and Bateman, 1990); (ii)and (iii) serve for the representation of perspective sequences, i.e. reiteration and collocation relations in discourse. One such relation is giwm by all pairs Lt.'t A 1,1:2 ('I.F sequences') which show the same eooecurrenee behavior (e.g., the sequences ()pert A Operl and Vib A V0 show l, he same eooeeurrenee behavior; both stand for strict repetition). Consider Tabh'. 1.</Paragraph> <Paragraph position="4"> LF sequences are dlre.cted, i.e. l,Ft A I,1,'2 ~ I,F2 A 4 \[f sevet'g:tl (silnp\[e 07&quot; conll)lex) l,Fs COltll)OS;l! a phrase ()r ;t clause (as, e.g., AntiMagn itlld SO COlllpt)Se ?7t{'I~OT {Tlju~'y), W(! separate these LF8 by a 'o' sign, For the theoretical background a.Itd furl.her deL,~tils of how IA,'s can |:,e ct-~lnposed wil.h each other, see the literature on Mea'ni'a 9 &quot;l'e:ct 7'heory; e.g., (Mel'(mk and F'olgub..re, L987).</Paragraph> <Paragraph position="5"> 1,1,' 1 . Moreover, Lhe I~xig(,(?llCe O~ I,F l A I,F 2 ill a language does not mean that 1,1&quot;2 A I.F I ix also awdlabhL '\['hererore, in LF sequences, one argument, is t, he 'hu}>' (.he point o\[&quot; dep+u'ture (or l, he expanded LI,') and the other at'gtllllelaL ix Lho 'hul) expattder'. Ilow a specilic LF e.an |)e cxpallde(I, i.e. which I,F Se(ltlellces a.re possible, depends individually on this 1,1.', and on whMl Ll:s are fm'ther awdlM>le for the enl:it.y the LFs are apl>lied I,O. (~Ollll)al'e , e,g., L\]le I,F seqtletlces t;llpJ, instant,ial;e the negated antonymy reiteration for Vo(forgelling) and l,he l,wo, whMt insl,a.nt, iat,e t.he same relal, i,:nt for what he says is not h'Pte.</Paragraph> <Paragraph position="6"> Apart fi'om the reiteration or collocal,km relation it st.ands for, an I.F s,~(lllellce is rurther characl;erized by its possible syntactic roalizal, ions and its functlonM COIll,elIL</Paragraph> </Section> <Section position="2" start_page="370" end_page="371" type="sub_section"> <SectionTitle> 2.2 Syntactic Realizations of I,F Se- quences </SectionTitle> <Paragraph position="0"> As a ruhL an LI,' sequence is reMizahle by severM C/li\[l~rent syntactic constructions. Ilow these eonst.rucl.ions can look like ix predel, crmined by each IA&quot; sequence individually (and by the information to be comnumicared). I,'or example, Opert A Opert (more precisely, strict repetition) is in general realizable only as a parataclic eomplca: clause; of. Ilave a look at it; please have a look. In cont.rast., \['or examph!, ()perl A Magn o Su ix realizable when applied to, e.g., decision by nil synt.act.ic const.rucl.io,ls possibh'., of.: (8) a. ,Iohn made a decisim*; this deci,qiou was important to him (parata(:t.ic cf,,l,plex clause); b. John made a decision, which was importanl to him (hypota.ctic complex obtuse); c. The decision, which John made, was important to him (embedded clause); d. Join+ made an important decisim~ (siml)le cla.use); e. John's recently made importanl dcci,don (phrase).</Paragraph> <Paragraph position="1"> The reh!wmee of syntactic varial,ions for the realiza,lion of discourse sl.ructure relations is well known, ef., e..g., (l\[ovy, 1!)93).</Paragraph> </Section> <Section position="3" start_page="371" end_page="371" type="sub_section"> <SectionTitle> 2.3 Functional Content of LF Se- quences </SectionTitle> <Paragraph position="0"> Semantics, lexis, and syntax of LF sequences do not provide sufficient criteria for the choice of one sequence over all other comparable ones. These criteria nmst be provided by tile functional con lent we associate with each sequence (or reiteration and collocation relation, respectively). The flmctional content of tile reiteration and collocation relations listed in Table 1 is presented in Table 2. '~ strict repetition issisting~ restatement</Paragraph> </Section> </Section> <Section position="5" start_page="371" end_page="372" type="metho"> <SectionTitle> 3 TOWARDS LEXICALLY BIASED DISCOURSE RELATIONS </SectionTitle> <Paragraph position="0"> Due to their functional content, El,' sequences serve.</Paragraph> <Paragraph position="1"> ~s instantiations of individual discourse structure relations. In our work, we suggest that these individual discourse structure relations can be organized cohe,'ently in terms of the fimctions anti semantic distinctions they represent. In accordance with the claim that the availability of specific LF sequences is dependent on the entities the LFs are applied to, we furthex suggest that this organization must be done individually for each predicative entity (el. Wanner, 1994).</Paragraph> <Paragraph position="2"> Based on this, we define taxonomies (one for each predicative entity) which have been inspired by tlalliday's proposal for grouping interclausal logico-semantic relations (el. Ilalliday, 1985). l\[ow such an organization carl be realized efficiently using inheritance teclmiques is described in (Wanner, 1992).</Paragraph> <Paragraph position="3"> SThls is not to say that these functions are the only ones that are possible Although our model is not restricted to interclausal relations, two features o\[' lIalliday's proposal are wtluable to us: (i) that a Iogico-semantic relation 'expands' one wording by an another one rather than connecting two given wordings and (ii) that a logico-semantic relation can be further decomposed with respect, to its: 1. semantics, 2. syntactic realization, 3. communicative structure, and 4. with respect to the speaker's intention, which motiw~tes the selection of this relation during the text production process.</Paragraph> <Paragraph position="4"> In what follows, we discuss first the general taxonomy of our 'expanding' discourse structure relations for processes and then the decomposition of the reh> tions along these four dimensions, l?ollowing the conventions in R.ST, we call the expanded part 'nucleus' and the expanding o,e 'satellite'.</Paragraph> <Section position="1" start_page="371" end_page="372" type="sub_section"> <SectionTitle> 3.1 Taxonomy of Lexlcal Discourse Re- lations </SectionTitle> <Paragraph position="0"> A taxonomy of lexical discourse, structure relations is to be understood as a hierarchy of alternative choices of increasingly delicate relations. The most delicate relations are I,F sequences represented by their functional content. The top level of the. taxonomy represents, thus, the most global types of exI)ansion. In accordance with (llalliday, 1985), these are F, Lalm-RATION, MXTENSION, and I,\]NIIANCEMENT. ELAIt()I1.A-TION subsumes all those, expansions which ensure a deeper understanding of t,he meaning comnmnicated by the nucleus wording. A deeper understanding or the nucleus wording is ensured by reslaling, refining, or clarifying it (the next level of ELABORATION in the taxonomy). For example, all reiteration relations are of the I,;LABORATION type.</Paragraph> <Paragraph position="1"> The EXTENSION expansions extend the meaning comnmnicated by tile nucleus wording. This can be (lone by introducing a new constituent that is related to what has linen said ill the nucleus, by adding a new action of I.he known constitueuts, etc. Beginning extension is, e.g., an EXTENSION.</Paragraph> <Paragraph position="2"> The ENIIANCIi:MI,'NT expansions qualify the meanlug conmmnieal.ed I)y tim nucleus wording by adding a reference o\[&quot; causation, time., location, l;qanne.r, mode, etc. An example of F, NIIANCEMENT iv causal enhancement.</Paragraph> <Paragraph position="3"> figure 1 shows ill lllOl'e detail tile ELABORATION fragment of the taxonomy in network tbrm. According to this figure, ILESTA'PI,3MENT can be realized as a conlraslive, a generalized, or as a repealing reslalemenl, respectively. As shown ill Table 2, CONTII.ASTIVE RESTATEMENT corresponds to tile reiteration negated antonymy, GENEItAL1ZING II.ESTATE-MENT to superordination, respectively. ItEPl,',ATING RESTATI,;MENT is further insisting, clarifying, illustralive, pictoresque, etc. (see again Table 2 for corresponding reiteration relations).</Paragraph> </Section> <Section position="2" start_page="372" end_page="372" type="sub_section"> <SectionTitle> 3.2 Decomposition of Lexical Dis- course Structure Relations </SectionTitle> <Paragraph position="0"> As presented in Figure 1, the relations are still too global to be useful for lexical choice. Consider, e.g.</Paragraph> <Paragraph position="1"> ATTI:tlBUT1ON - it subtype of the R1,;HNI,',MF, NT reliLlion; it allows for various decompositions with resi)ect to all h)ur dimensions mentioned al)(')ve:</Paragraph> <Paragraph position="3"> TItlBUTION, e.g., of a process, of one of the participants of this process, or of one of the circumstances of this process; if ATTIUBUTION of ;t participant (let's slty tim ACTOR) is llleltllt, it is still undetermined what lind of attribution this is (e.g., a one which enables the actor to engage in the process, a one which l)rew~nts him front engaging in this process, etc.).</Paragraph> <Paragraph position="4"> * Syntactic realization; how the wu'ious ATTILI-BUTIONs Call be realized syntactically del)en(Is on the senlantic and \]exical properties of the infer marion to be eommunical, ed. For exanll~h!, 111o71ica flew 1o Ilaly; it was a very pleasant journey is also realizable as a subordinated clause (Mortice flew 1o Italy, which was very pleasant); its ;t simple clause (Mortice had a very pleasant journey Io llaly); and as a. phrase (Mortice's pleasant journey lo Italy).</Paragraph> <Paragraph position="5"> * Communicative structure; the corrlnl,micatiw~ structure of ATTRIBUTION Varies depending on the order in wl,ieh m|ch.'us and satellite, are realized. Cf., e.g.: Moniea flew 1o \[Zaly; it was a very pleasant journey vs. II was very pleasant, e.g., ;t justification of what has bee.u (-omnmnicared in tile nuchms as in John failed the exam; it was very dijlicull; a consequence of it John has beeTz shot - he ist dead, el, c.</Paragraph> <Paragraph position="6"> 'Fhe increasingly delicate specifications achieved by decomposition are also represented hierarchically in network fl)rm; one network for each dimension.</Paragraph> </Section> </Section> <Section position="6" start_page="372" end_page="373" type="metho"> <SectionTitle> 4 GETTINC, TIIE RELATIONS AC- CROSS </SectionTitle> <Paragraph position="0"> The lexieal choice process, which makes use or the discussed discourse structure relation taxonomies, and tile representation or lexical resources arc described in detail in (Wanner, 1992, 1994). lh, re we focus on the interface between the first, level text planning and the lexical choice n|odule; and ou the output as prodt|ced hy the lexieal choice n|odule.</Paragraph> <Paragraph position="1"> The ecmllmlatioual fr;mu~work in which our model has partially been implemeI|tcd, is the systet||ic text gc|lerator KOMI,:'I' (Ibtl.eman ct al., 1991 ). One source o\['constrainl.s l'or the. first hwel text orgm,ization comes ill KOMI&quot;T fl'Olll all It.S'l'-l)ased pla|Hler, t; The outpul, of this Iflanner is a collection of case frame.s with RSq&quot; relations hohling between them as shown in Figure 2.</Paragraph> <Paragraph position="2"> Starting from a text phu, of this lind, I,he lexical choice module traverses a multilayered collection of networks (one of these layers is given by ;~ taxonomy of lexical discourse structure relations disc||ssed), l)uring the I,r;~versal, the text plan is transformed into n lexicalized Partial (;','a~,matieal /~truclure (pf~s); 7 it is called 'partial' because it contains precisely that an|ou||t ofgran|matic.al infornmtion which is necessary (;lh:ceut, dewdopmcuts of this phmtmr are described in (l levy el eL, 19,q2).</Paragraph> <Paragraph position="3"> 7A l'(~s corrcsponds~ roughly speaking, to the Partial Surface l,'~tnctional Description (I'SFD) specilicatiml in the COMET syst, mn (McKcown ct el., 1990).</Paragraph> <Paragraph position="4"> process: LiE\[spelling: &quot;lle&quot;\] &quot;1 LEX- \[verl': + \] / \[\[l Pl~I MARY ~saye* MAN \[spelling: &quot;n.m&quot; \] - .': \[\]LEX- \[ ........ + J/ ttheme: \[\] 3 g \[spelling: &quot;be&quot;l &quot;1 /p ....... LEX-BE\[ve,,t,: + J lying; he is a liar for lexical choice. The PGS iS passed to tile grammar (a systemic grammar of Gerlnan; el. Teich, 1992) for final syntactic realization. Figure 3 shows a sample pos encoded ;m a Typed Features Structure (el. Bateman el al., 1992).</Paragraph> <Paragraph position="5"> The tirst and the most important task in tailoring the text plan to linguistic resources is to find a lexieally biased discourse structure relation for the Rs'r relation specified in the text l)lan. The search is done in accordance with the filnctional content, the intention of the speaker, and the contents of the arguments of the RST relation. If tile RST relation connects unrelated case frames 8 (as, e.g., EVIDENCE in In winter, the days are short. It is getting light late and eaHy dark.) these case frames are realized independently without being connected by a lexical discourse structure relation. If the cruse frames are related, tile following three variations are possible: (i) An RST relation instantiation coincides with a lexieal discourse structure relation; as, e.g., the instantiation of RESTATEMENT in the following rudimentary text plan coinsides with our RESTATEMENT: :verbiage, :manner, , , .o :~ituatiQn))) . If so, tim suDciassmeatlon of the lextcal discourse structure relation deter,nines its final realization. For example, the above text plan could be realized as a GENERALIZED II.I,~STATF, MI,~NT: S'vela fl'l'islerle; sic sayle elwas .qanz leise lit. 'Sveta whispered; she said something very quietly'; an INTENSIFYING RESTATE-MlgN'r: Svela sagle ehvas sehr leise; sic hauchte es kaum hb'rbar hin llt. 'Sveta said something very quietly; she breathed it hardly audible', etc.</Paragraph> <Paragraph position="6"> (ii) An RST relation instantiation subsumes several diss Case frames are considered to be unrelated if between them or one of their roles no identity, is-a, causer, location, etc. relation holds.</Paragraph> <Paragraph position="7"> tinct classes of lexical discourse structure relations; as, e.g., the instantiation of the aST relation CONTRAST in (this plan is also highly simplified): may be realized either as CONTI~ASTIVE CI,ARIFICA-TION (ga) or as CONTR.ASTIVE ENIIANCEMENT (,Oh): (9) a. (2aul is entirehj occupied by the I~omarts; well, not enti~vly ...one small village still hohls out.</Paragraph> <Paragraph position="8"> b. Gaul is uhnost entirehj oecvpied by the l?omans; but one small village still hohls out.</Paragraph> <Paragraph position="9"> In this case, tim taxonomy of lexical discourse structure relations is entered at a relatively general level (in the worst case at TOP).</Paragraph> <Paragraph position="10"> (iii) An lIST relation is not captured by our taxonomy (as, e.g., CONCI,ISSION). Then, the corresponding ease fi'ames are treated as unrelated (see above).</Paragraph> </Section> class="xml-element"></Paper>