Resolving syntactic ambiguities with lexico-semantic patterns: an analogy-based approach

Resolving syntactic ambiguities with lexico-semantic patterns: an analogy-based approach(*) Simonetta Montemagni l'm:, O. La sas via, d(;I l:~orgl-wJ;to 35 I)isa,, 561100, ITALY siln oq*) i ] c. I)i. cn r. i 1; Stefano Federici Pa.r.O. La sas via, ([el 13orghetto 35 I)is~t, 56100, H'ALY .~teth.no~,!ih:. pi.cnr.it Vito Pirrelli ILC-(?NR via (lell~t l:~ggiola 39 Pisa., 561126, ITAI,Y vitoOilc, pi.cnr.it Abstract A system for the resolutio~ of synLa.(> Lie a.mbiguities is illusl;ra.teel whi(:h op era.tes on ,norifl/o-synl;act;ica.lly a.u:d)igu- ous st, I~,iect-objecl; a.ssig,, nmnts i, 1Lal Jan a.ud tries t.o find the .,ost likely aua.lysis (Ill [;[/e I)asis ()[' I;h(: cvid('m:c co,,ta,ined it, a knowledge Ira.so of linguistic data. a, ut, otna, tica.lly ('xtra,et(~d from on-liue re'.- sources. The system works o. I;he ha.sis of a. set of sl.ra.ight;forward analogy based princil)les, ll;s performa.nce on a sulssta.n- tial corpus of l;est da.I;a. (~xl;ra.ct;e(I from real texts is des(:ril)ed. 1 Introduction In this pal)e.r, a syst(;n, for the resolut;ion of syn- Ca.el;i(: ambiguities is illusl:rated: Se,SOK- the SEl:naNtic Sul)je(:l;-OI)j('x:l: (lisaml)igua.(.ol{- ()per- ales o,t n,orpho., synl;a.cth:a.lly aml)iguous sul)ject- object assignmenl.s in I t;a.lia.n a.,(l tries to tind the most likely analysis I)y using the (widence con- ta.ined in a. knowhxlge ba.se of linguistic da.ta, auto- ma.t.ically e.xtra.(::ted firom machine reada.I)le (lictio- uaries (Ml{.I)s), bolJ~ ta,xo, lomie in['orma.tion and ('xaml)le s(mt;e.(:es. The syste, n works on the I)a, sis of a set o[' st.ra.ightforwa.rd a]m.logy-lm.sed 1)tin - ciples whi(:h ha.ve I)e(m used for a wide range of NLI ) a.lfl)licatio,s (I)irrelli el: a.l., 1!).()2; Monte- magni et a.l., 1994; I,'e.derici et al., 19()6). Both inherent semanti(: l)rOl)erdes of words (as embod- ied by taxonomical relationships) and word (listri- I)utiona.l l)rOperties (as a.ttest<;(I in cxanq)le sen- tences) are exl)loited as a clue l;o the most likely '1 b.lecI. {.)l>j(,,t. /~8~iglltttc:n(. (S()A). We start, with a.n illustration of the pa.rsing problem, I:o move on to a (:onsideratio. o[' the na- ture of the lexieo-sema.ntic knowledge usa.Me for its solution. SenS()l/.'s Knowledge Ba.se (KI3) is then described, l.ogel, her with the fimcdon which projects mnbiguous SOAs onto KB in the search for the best ca.ndidate a.mdogue.. 'Pwo (liffere.nl; tests of S(mSOll.'s perforln~mce are illustra.ted and discussed in some detail. I,'inaJly, further improve- ments a.re sketched a.nd other possible a.pplic~-~tions of tlm system envisaged. 2 The problem A crucial problem in pa.rsing Italian is tll(; assign- menL of subject a.nd object relations to sentence constituents. It, is ot'te.n the case that grmmna.l:- ieal relations cannot be a.ssigned unambiguously on the basis of morpho-syntactic informa%ion only: in the sentence il bambino leggc il libro 'the child reads the book' agreement information is not de- cisive for SOA sin(y, both nominal constituents agree with the w;rb. On the other hmtd, word of der informa, tioll cannot be relied on con(:lusively due to the freedom allowed in the ordering o[' sen- tem:e constituents in Italian, where virtually all permutations of verb, subjeel; ~utd object a.re pos- si hie. The and)iguities sl;emming fl:om this []:e+'dom are ubiquitous and represent a problem fbr a.ny NI,P …

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