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<?xml version="1.0" standalone="yes"?> <Paper uid="C96-2127"> <Title>An HPSG-Based Generator for German An Experiment in the Reusability of Linguistic Resources</Title> <Section position="4" start_page="0" end_page="753" type="metho"> <SectionTitle> 2 Available Resources 2,1 The FUF Generator </SectionTitle> <Paragraph position="0"> li'UF (Elhadad, 1991) is a surface generator for naturM language based on the theory of flmctional unification grammar (Kay, 1979). It employs both phrase structure rules and unification of feature descriptions. Input to I&quot;U F is a partially speciiied feature description which constrains the utterance to be generated. Output is a flflly specified feature description subsumed by the input struel,ure, which is then linearized to yiehl a sentence.</Paragraph> <Paragraph position="1"> (~rammar and h;xi('.on are specified as one large \['eatm'e descril>Cion, containing aC h;asC one dis.junction (given t>y Che alt keywor<l) ranging over the pllrasal and lexical cal;egories of l;he gr;umnar. The feature, cat is used Co indica/,c t, hese cat, e-Aeries. 'Fhe fealmre lex associat.es strings wil;h lexi<'at (;m;egories. '\['he trivial grammar of Fig. I exemplifies the layout of a FU F grammar.</Paragraph> <Paragraph position="3"> }'oinCers are used Co enforce sCl'llcl;tlre sharing and provide a ~neans {,<> percolaCe informaCion within a \[eaCm'e sl;rlleCllre.</Paragraph> <Paragraph position="4"> I,'ll\],' provides the means Co specify a sul)sump don or(Jeriug of l?lpeS, whi<'h is useful {.<) express gem;ralizaLions, an(\[ it illa(:ro 1He('halliSlll.</Paragraph> <Paragraph position="5"> C, eneraCion sCari;s fl'om an undersl>e('ified input fe=al, urc struc/,ure, li'UF unifies the grammar inlo the input sCrucl, ure, i.e. enricln:s and furl.her constrains iC. Alternatives are explored sequentially until one I>ranch succeeds. Thus Cite inl>ut st;rue-Cure never ('.ontMns all@motions.</Paragraph> <Paragraph position="6"> When unilieaCion aC the <:urren(, level is com\[)leCe, i.e. noChing furl, her can I)e added to the int>ut sl, rucCure, every substructure of the input rei)resenCing acat, egory is recursively unified wil;h I;he gral~H\[nar. This process is re\[>eaCed breadth tirst mltil all <-onsCituents are h'.aves.</Paragraph> <Paragraph position="7"> To det, erinine whi<:h substructures have. to be processed rceursively FUF employs two methods.</Paragraph> <Paragraph position="8"> The defaull; strategy (;ollecCs all subsi, rucl, ures of Chc current level having a cat feature, l';xplicit specification o\[&quot; subconsf, il;uents is also l>ossible via the special Feai.ure cset (<:onsCiCuent set). If cuet is presenl,, FUF performs recursion on these exl)liciCly given subsCruct, ur<'s only. E.g., \[,he default sCraCegy operates on (;ategory s in Fig. 1 as if (cset (subj pred)) had |teen specitied.</Paragraph> <Paragraph position="9"> When specifying (cset (pred)) only, no recursion wouht be performed <)n subj.</Paragraph> <Section position="1" start_page="752" end_page="752" type="sub_section"> <SectionTitle> 2.1.3 Linearization </SectionTitle> <Paragraph position="0"> The recursive unification process handles only t,he dominance relations of 1%c grannuar. In order to a.c(:ounl; for linear ordering of l, tlo resulting I,ree shaped feature structure, FUF performs a linearizal;ion \])l'OC(~S8 a~0,e.t&quot; unification has linishcd. IAnear l)rac.e(hmc.c of ('.onstituenCs is sl)ecitied in the. grammar using (;he special feal;ure pattern.</Paragraph> <Paragraph position="1"> Only constituents mentioned in a pattern are realize(\[ during linearizalfion. Thus, the simple grammar in Fig. l has Co I)e enriched: (pattern (subj pred)) has Co be a.dded at (cat st, (pattern In)) has 1,o he ad(le(\] al~ (cat apt and (pattern Iv)) is needed aC (cat vp). I,exic.al categories don't, need a \[)att, crn feature.</Paragraph> <Paragraph position="2"> I>atterns need not spe(:ify an absolut, e ordering.</Paragraph> <Paragraph position="3"> E.g., (...a ...b ... ) q)eci\[ies t,haI, consCii;uenl, a Ires Co precede b. More sa(:h Imrl, ial pal,t, erns ntay Ice specified, i)aCtern unifical, ion leads Co all \]egM constiCuenl, (:ombinal, ions.</Paragraph> <Paragraph position="4"> I,inearizaCion traverses the ere(% ex|,ra,(:Cs the M,rings foun(l in Che lex \['eaCnre o\[&quot; the leaves, and \[lai;Cens gl,is sCruclure a.ccording Co (;110 pattern directives fen u(l.</Paragraph> </Section> <Section position="2" start_page="752" end_page="753" type="sub_section"> <SectionTitle> 2.2 The HPSG Grammar for German </SectionTitle> <Paragraph position="0"> In IIPSG (Pollard and Sag, 1987; I)ollard and Sag, 1994), i,he fundamental objects o\[' linguistic anMysis are signs modeled by typed fea(,ure strucLures and ('.onsCrMned by globM 1)rmciph;s. II I'S(\] <lees uoC employ phrase strut'.Cure rules. Instead, very general dominance sc\]mmat, a are given. Which ar gmncn/,s a lexicM head takes is lexi(:ally sl)e<'iii(~d iu its SIII~CAT list. Also adjunction is st)ecili<M lexically; t,he ad.iuncC is seen as the semanl,ic head which selects t, he kiu<l of signs i(, modifies, (,it(: modified sign relnains Lit(; synCa(:t, ic head <)f the rcsulCing phrase. \[,ong dis(;ance del>endcncies a.r<'.</Paragraph> <Paragraph position="1"> handled in Ill)S( |not; in terms of nlovcment; ImC via structure sharing of the values of a SLASH I'ea-Cure \])er<:olaCing the &quot;moving&quot; consl,iCuenl,. The grammar for German follows the version (>f IIPSG giv<;n in (Pollard and Sag, l,<)!)4) rat, her si:rit:l.ly, deviaCing only in the following aspects: * The Sub<:al, egorization l)rineil)h; is given in a binary bra.nching fashion.</Paragraph> <Paragraph position="2"> * '|'lie arglllllell|, struct, ure of h'.xical heads is enri(:hcd. Thus gcncrMizadons ronc<'.l'ning (:ase a.ssigntnenC att<l argmnen\[; reduci, ion I)\]ienom ena (:an be <:el>Cured in a principled fashion (see Ileinz and Mal, iasek (1994)).</Paragraph> <Paragraph position="3"> * Verb second posid<m is handhxl by a mechanism resembling Cite notion of head movemt:nt, of (\] B-Cheery.</Paragraph> <Paragraph position="4"> 2.3 X2MorF X2MorF (TrosC, 1991) is a morphoh)gical (-<tin-I)<ment bas<;d on two level morphok)gy (Koskenniemi, 1983). In l;wo-level m<)rphoh)gy mor 1)hol)honology is treated by means of rules (,hal, The process of recasting the original ITPS(\] structures in the FUF tbrmalism can best be described by exalnples. In Fig. 2 the htPS(\] representation of the German verb gem (walks) and it,s representation in t?UF is shown, exemplifying the following mappings of HPS(\] onto FUF: a.s proposed in Pollard and Sag (1994) the convention of Pollard and Sag (1987) to subcategorize for signs is adopted.</Paragraph> <Paragraph position="5"> * Instead of a list-valued SUBCAT feature the feature args is used. The correspondence between (syntactic) arguments anti semantic roles is established by placing the constituent under a feature corresponding to its semantic role. Thus list manipulation is avoided and the structure corresponds more closely to the input specification (given in a language based on SPL (Kasper, 1989)).</Paragraph> <Paragraph position="6"> * The NONLocal feature is dropped. Slash extraction is handled differently.</Paragraph> <Paragraph position="7"> It should be noted that this entry does not col'respond exactly to the actual representation in the generator, it serves simply to illustrate the basic ideas underlying the transformation. The actual implementation additionally allows for * the specification of arguments via external macros, accounting for a more principled treatment of case assignment, argument reduction and slash extraction; * a ditferentiation between lexemes and stems to account for a treatment of inflection by the morphology component.</Paragraph> <Paragraph position="8"> The representation of phrasal signs in IIPSG parallels the one of lexical signs; an additional feature DTR, S carries the subconstituents o\[&quot; the phrase. One of the daughters is the head of the phrase (IIEAD-DTIt), its head features are identical to the head features of the phrase (llead Feature Principle). The other daughter may be either a cornmap between the lexieal representation of a word arm its surface fl)rm. Morphology proper on the other hand is viewed as a sirnpte concatenation process governed by a regular grammar.</Paragraph> <Paragraph position="9"> X2MorF augmertts standard two-lewJ morphology in two ways. First, it replaces the contimmtion class mechanism with a feature-based word grammar and lexicon. This is an important prerequisite for its use in a \[hature-based sentence-level processing system (see Trost and Matiasek (1994)). Second, it allows for interaction between two-level rules and word grammar facilitating the formulation of rules for non-concatenative morphol.actics like umlaut.</Paragraph> </Section> </Section> <Section position="5" start_page="753" end_page="754" type="metho"> <SectionTitle> 3 The Integration Task </SectionTitle> <Paragraph position="0"> Although the main components to be integrated fulfill reusability requirements (FU F being a fairly general and modular generation engine, the HPSG grammar being a declaratively written resource), integration of these resources into a unified system couhl only be achieved after suitable adaptation. The morphological component of FUF is very restricted. Thus it needed to be replaced by X2MorF. The available German word level grammar of X2MorF was rewritten to conform to the feature structure notation employed by FUF. The two-hwel part stayed unchanged. More substan|ial changes were required to adapt the HPSG granLmar. Not only syntactic adaptations to another feature formalism were needed, but also the olmrational characteristics of' FUF had to be accounted for. Also some of the phrase structure information generalized in the form of principles could be &quot;compiled&quot; into phrase structure rules.</Paragraph> <Section position="1" start_page="753" end_page="754" type="sub_section"> <SectionTitle> 3.1 HPSG in FUF </SectionTitle> <Paragraph position="0"> First experiments to implement ItPSG in FUF rather directly showed inetficient runtime behavior. Since most grammatical constraints in IIPSG are expressed via structure sharing, and FUF uses pointers to indicate coreferences, most of the processing time was spent in following pointer chains through deeply nested feature structures.</Paragraph> <Paragraph position="1"> Thus the structures have considerably been fiattened and some aspects (most notably SUBCAT and CONTent) have beet, encoded differently.</Paragraph> <Paragraph position="2"> pleiNei'll,, a,u ;tdjurlet,, ;i. marker or a filler (realizing l,he shcsh l'e&t,lll'e (if l;|le tt(;;ul d;-:uighl, er). l!\]a('h consl;ituenl, sl;rHcture is (;onsl_d'~:titl0d by {/.\[1 aSsoci;d.e(l sel, or (h)mimmce s(:heniai, a and princillles.</Paragraph> <Paragraph position="3"> iII)S(l (lis/,inguishes be/,ween s,lz/Ls/,a'#l, bive (',aJ;egories (Sllch ;1.8 ilOllil8 or ver|)8) ~md ,\[:\[ul, clio,l, al (-a,tegories (e.g., (leterininers). Siliec rliilcdonal ea, l,egories COl'l;(:.si)ond (;0 ('\[osed word (;lasses, in die I&quot; UF iinl)leHlcnt,~fl, ion (,hese ('at, egori(:8 are (:elf|-I)ile(t into phrase sl,rlletllre rules.</Paragraph> <Paragraph position="4"> '\['hc s.}Litle apl)roa, ch , i,e. t'a.(:t,oring Slll)('.a,teg:oriz~d;ion hiforl:n~l;hm hire l)hrase sl, rllcl;lil'e rilles, is l;~ken wi~Iri auxilia.ry a.nd modal verbs and with t)tienoilielia, which t\[t;l,y well be rega.r(led as 1;he lllanirosl.a.lJoli el ;.i, flin('.l, iona, l cal,egory, l)u/. whi('h are ilOl, ext)resse(/ by lexical it;elns bill; by speci;d (;oltst.i|,\[lelil, or(lerillg (e.g., verb se(:olld l\[osit, ion in (le('.la..ra.(Jve i\[i;~ili el;roses).</Paragraph> <Paragraph position="5"> Th(' i, roatineni; o\[&quot; axljunct, ion in I.he I&quot;U l&quot; iinp\[e-inen/;ai:ion rellects l;he rel)resent~d, ion of lmodi\[iers ill the. inl)\[lt; \]glllgll;i.g(':. The llPSG vi(~w of ;l.li ;IAI.i,li-'l; ;\[.s l,he seln;ml;ic head selecl,ing I;ho sign it |lied|ties, is changed 1;o the view l,hat adjililCl;s ac.l,</Paragraph> <Paragraph position="7"> M a,uy c, onsl, ra, it\[t,s exl~resse\[t in 11 PS(\] by Iriea, liS of priilcipl(':s (e.g., dOlrliil;'~i|ee s(;\[lell\]~t,;l.) :q.l'e ;i,lready built into t,h(&quot; phrase sl,r\[i(-l;llre r\[ll(!s (:Olilpiled el|l; el I, he origin~J gl'a,i\[lll\];:u'. 'l'here re-in;tin, however, I,he inosi; cet\[{,l'al lll'S(~ princ.ipies eonsl, r;~iliing all phra.s0s an(I ensuring tim i)roper ili\['\[)rm~ttioll sharing l)el,wo(`-n rnol;her ~uid tie~ul (laughl;er. These are insert, od int, o (,he gra, lllnla.r al; l,|le level (cat phrasal-category). The 1)ra.ii(;hes dispai;(;hing 1,()parl;i('.uiar phrase l, ypes ar(' st)e('ilied l;fl, er in ~/,Ii emi)eddod disjuncl, ion.</Paragraph> <Paragraph position="9"> l;'ig\[u'e 3: lIPS(; l'rinciph;s ill li'l\]l '' Ilow(wer, o\[\[e irriporl;anl; t)rinciph~ of ll PS(\], the Sub(::~A;egorizal, ion I'rineil)le ei'iSlll'illg ~he i)rol)er rela.l,ionshi 1) bel;we(m tim a, rgllmenl;8 subcaA,egorized for a, lld the eonstil,uenl, strllg|.llre el I;he phrase 81ill nee(is I,o \])e ;%(;eOlltll, e;d for. Ilow t, his const;rn, inl; is /nel, will I)e discussed next.</Paragraph> <Paragraph position="10"> 3.1.3 Cont;rol S f, ra f, egy FUI&quot; el\[lploys a, t, op-down l\[roccssinp; scheme (Iriven by l, he synl,;t(:l;ie (;a.I;(:gory ()1: l;lie lnol,her. This (-ont;rol sl;ra, t;egy is init(iequal;(&quot; when die consl,ilJuel\[t st,ruc.I ure is Sl:,e(:itied lexica,lly hy t;he lle;:,A a,n\[l l,hus uldcnown u.I;il l, ll(', head is eXl);~il(le(l. llPS(\] lends il;self best to heiul-driven, t)otJ;olu-u l) i)roc.essiugl a,l, le;-~sl; for genera, l;h)l~l. ,':;ilt(:e t, he COlltrol regil\[l(; of b'lJ l&quot; (:anllol, b(' (:ha31ged in prhl(-iph'~ (only delay lrle/,hods a, re awdli~ble), l, tie grPdicilri;u' it:self has 1o aCCOlltll, for :-ulequa, l,e processil~g ch,u,racterisl;ics. This i'rie,~l, ns, l,h~t, l,hc h;xicon drive. apf)i'oa.ch has I;o 1)e einula/,ed wil,hin t, he g,i'a.Iliiliar, based on |;he oper;tl, ionM behavior of FUF.</Paragraph> <Paragraph position="11"> The tmsic ido;~ for rcMizmg head driven pro-.</Paragraph> <Paragraph position="12"> c.(;ssing behavior is 1,o ilse Idle cset a,nd pattern special at, t.rib ul, es of F U F in an asymmetrical fashion. Ge.eral, ion of a phrase sial'is by realizing i{.s head-dtr. 'l'hel'e\['ore only the head daught.er is specified ill IJm consl;it, uenl, set, o|' tdlc phra,sc.</Paragraph> <Paragraph position="13"> Once l.he \[cxica.l hea.d of l.he phrase is general.ed, its ;-trglliiieill, list, is a(-I;iwfl,ed using l, he defaull, re (;llrSiOll sl;ra, t, egy o\[&quot; FUF (8inee no cset atl;ril)ut(? is l)l'esent). The lexie;dly 8t)\[;(:ilie(I ;trglltnenl.s ;u'e uow genera%ed in ~* (virtually) bol;|,onl u l) l'ashion.</Paragraph> <Paragraph position="14"> ,ql;rll(;t.llre sh;u'ing lmr('oliLi;es l;he args upwa.r(ts 1,() the lJiras;tl level, where l;hey m'e l,tieri re;dized via Idle lia.l;/,erl\[ \['e;q\]Air(~. The basil; iii(ich&\]:liSll\[ o\[' ell-</Paragraph> <Paragraph position="16"> (:oding this processing st, rategy in tim gr;tt\[llila.r is given in Fig. 4. If flmcl;ional categories are 1)resent.</Paragraph> <Paragraph position="17"> in ~L phrase, /,hen the ~q)l)roprial, e slots have lo he 81)e('ili(:(l and ;~xhled to cset a, nd pattern.</Paragraph> <Paragraph position="18"> Thus Ge shape of I.ll('. resull.ing phrase la.rgely depends o, the kind of argutnenl, s it, s lexical head adtnit, s. In order to realize its argutnents, every word aMe, 1;() acl; as th.:: head of a, phra, se Ira8 1;() provide ;t 8ynt;act, i(&quot; a,n(l ,sema\[d;ic Slw~cili('at, ion (:4 i/,s a, rgumenl,8. 'this SF.(;(-ili(-;~l;i(m a,180 has l;o a,(;c,:mnl; for long distance phenomelm, i.e. (:xl;r~(;I;ion of a.ll arg/llllenl; (e.g., wh lnOVel\[lell(,), l,'url,hern\[ore, wu'ia, I;ions of case assig.irlent (e.g., in I)assiviza l,ion) Inwe 1,o be ;~ccount(xl lot.</Paragraph> </Section> </Section> <Section position="6" start_page="754" end_page="756" type="metho"> <SectionTitle> 3.i..4 Argmne:n.t; St:rm'~m'c, Encoding </SectionTitle> <Paragraph position="0"> Although a, large amount ()t' infl\[rmal, ion has I,o be 8(x)re(l hi (:tie h:xh;on, a. COlllp~-l(;\[, ;(lid easily )uaiitt,~fin~fl)le s/,rucl;ure of (,tie lexicon is a eruchJ requh'emenl;. There\[ore ext;ensive Hse has been inade of \[&quot;UPs external liiacros.</Paragraph> <Paragraph position="1"> Fig. 5 stiows l, lic a(;l;\[IM ellcOdil\]g of the lexica, l entry for &quot;warlen&quot; (&quot;wait&quot;), 8ubcategorizing for all acl, or a.nd a pal, ienl;..qynl,;~ct, ic resl;rict, ious on i, lie ;/,i'glllii(;lll, a, re given hy illaoros, pp-allf-acc (~Xl)a, nds I;o a 1'1' wii;h l:U'el)oSition a'uf a.lid ILc-('.usa.l,ive case, IJie realizal, ion of die si, r\[let, ural ~/l'I_~lll\[lellt) llp-ext-da (l('F, en(/s on whel;her i\[rgll- null ment reduction (i.e. passivization) has to be performed or not (for a theoretical background see Heinz and Matiasek (1994)). In active contexts it becomes the subject and receives nominative case, in passive contexts it may be optionally realized as a PPvon (see Fig.6).</Paragraph> <Paragraph position="2"> A mechanism common to all arguments and thus incorporated into every macro expanding to an argument specification is the extraction mechanism required to handle movement (see Fig. 7).</Paragraph> <Paragraph position="3"> At the phrasal level the argument which has to (;; try to fill slash by unification be extracted (e.g., in wh-questions the constituent asked for) has to be specified as tire slash feature of the args. Each argument must be checked during generation if it is unifiable with the slash specification, and, if so, it has to be made coref erential with slash. Otherwise, an appropriate pattern feature has to be produced to ensure the realization of the argument at the args level.</Paragraph> <Paragraph position="4"> 3.1.5 V2 and a Generation Example (\]erman is commonly regarded as an SOV language. However, the standard word order - a sentence final verbal complex with the finite verb as the last dement - is encountered only in subordinate clauses. In declarative sentences and wh-questions the finite element of the verbal complex occupies the second position in the sentence. Sentence initial position of the finite verb is encountered in imperative clauses and yes-no questions. In our grammar, the verbal complex is always generated in the standard order. To account for VI and V2 phenomena, a mechanism resembling the GB notion of head movement is imple- null mented. This mechanism flmctions analogously to the slash mechanism presented above. If a feature head-slash is passed to the verbal temple:, the finite verb is extracted, allowing the governing phrase to realize it in first or second position. The morphology component ensures that separable prefixes are left, in place.</Paragraph> <Paragraph position="5"> The vert)al complex is generated top down. 'l'he arguments of the main verb are generated lexicon driven, once the lexical head of the phrase has been established.</Paragraph> <Paragraph position="6"> Subject-verb agreement and nominative case assignment is handled via the subj slot which is coreferential with args: subj and - after argument generation -contains the subject of the sentence (of. Fig. 6). Verb second position (:an only be ensltred, if the constituent in sentence initial l)osition is nonempty. The slot focus is designed to hold that constituent. The constituent to be topicalized or, if not specified in the input, the subj is extracte<t via the slash mechanism (cf.</Paragraph> <Paragraph position="7"> Fig. 7). The interaction between top down category driven and &quot;bottom up&quot; lexicon driven processing is illustrated in Fig. 9, showing also the effects of the two slash extraction mechanisms.</Paragraph> <Section position="1" start_page="756" end_page="756" type="sub_section"> <SectionTitle> 3.2 X2MorF in FUF </SectionTitle> <Paragraph position="0"> For the integration of X2MorF into I:UF the unification engine used in X2MorF was replaced by I&quot;UF itself, and the existing word grammar and ~norph h;xieon were reformulated in the FUF forlaalism, and tim word form g('neration l, ask is now 1)erfontwd l)y FUI&quot; itself. The= two-level rules could be taken over in l, heir original form, only l.he morl)hologieal tillers had to l)e l, ranstaLed.</Paragraph> <Paragraph position="1"> A simph&quot; functor/argumenL scheme is suflicient for the word grammar. The possible eombinal,ions are given I/y the phrase structure rules of l.he morl)h grammar. '\['he affixes (fun('t.ors) may fllrthe.r restrict the arguments they may lie applied t,o. Fig. 10 shows an examph; of morphoh/gical e;Ltegorics reslIonsible \[br nominal inlh;ction. A u(mn stem has to be \[bllowe.<l by a case suffix which determines ease and number ()\[' the resulting noun form. 'l'he, head features of the argumen\[, are made availal)le t,o the functor via the arghead feature, thus <'aiM)ling the funcl, or \[,o subcateg<)rize for its argumenl; (e.g., by re(luiriug a certain inflection \[>ara.digm). ()he of tim l)ossible case suffixes is a troll morl)h inducing l)lural in a certain (;lass of nouns with (noun-paradigm null). It applies in all cases ex(:el)L dative 3 setting the umlaut feature, which U:iggers the two level rule forcing umlaut.</Paragraph> <Paragraph position="2"> An example is &quot;(larleu,&quot; with plural &quot;G:irlen&quot;. 'Fhe i\[iterface I>el, we, en synl.act;ic and wor<\[ tew'\] t~roeessing is provided hy the \]emma lexicon. It <-otd;ains l.he argulnent st;ru<;l;ure of t;he \]exemes aim links them I;o (l)ossibly prelixed) stems. The require<l syntactic features (>f a particular word form arc dct<'a'mined l>y the sentence level syntaeti<'. general,ion. 'Fhe \]elrlll:la lexicon l)aSSeS I;hese lhatures to the morl)hoh)gica\] level and l, he woM level gr~uttH, art, akes ca.re of sele(:l.ing the al)propri: at:e allixes. I)uring the finM linearizati(>li the cxl;ended ewe l<wel rules map l, he <:on<:aCenated stems and affixes to the appropriate surface strings.</Paragraph> <Paragraph position="3"> :~Thc boolca.n combinal, ions of ce.rtain fea.turcs ll~Lve Imcn spelled out in the type hierarchy.</Paragraph> </Section> </Section> class="xml-element"></Paper>