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Extracting Information from Participial Structures Kata Gábor, Enikő Héja, Ágnes Mészáros Research Institute for Linguistics, HAS 8th INTEX WORKSHOP, 2005 STRUCTURE IE system and its shortage: the problem of participles NPs and participles in Hungarian a possible enhancement of the IE system implementation in INTEX IE system input text (1-2 sentences of short business news) shallow syntactic analysis pre-defined semantic patterns (event frames) output: event frames’ slots filled by the elements of the input text the event, its participants and circumstances are identified Event frames Az ABN Amro Bank egyesül a Kereskedelmi és Hitelbankkal. ABN Amro Bank fuses with Commercial and Credit Bank. <event schema="owner_changed.fusion.6" roles_matched="3/3"> <rv role="member_company_1" pos="N" case="NOM" sem="company|institute"> <NP id="88" sem="company countable human institute"> <w id="0" class="DET" at="1-1" lex="az" case="NOM">Az</w> <w id="2" class="UNKNOWN" at="2-2" lex="ABN">ABN</w> <w id="4" class="UNKNOWN" at="3-3" lex="Amro">Amro</w> <w id="6" class="N" at="4-4" lex="bank" case="NOM">Bank</w> </NP> </rv> <rv role="_1" pos="V" lemma="egyesül"> <w id="8" class="V" at="5-5" lex="egyesül">egyesül</w> </rv> <rv role="member_company_2" pos="N" case="INS" sem="company|institute"> <NP id="118" sem="company countable institute"> <w id="13" class="DET" at="6-6" lex="a" case="NOM">a</w> <w id="15" class="ONADJ" at="7-7" lex="kereskedelem" case="NOM">Kereskedelmi</w> <w id="17" class="CONJ" at="8-8" lex="és">és</w> <w id="19" class="N" at="9-9" lex="hitelbank" case="INS">Hitelbankkal.</w> </NP> </rv> </event> Mapping syntax to event frames SYNTAX EVENT FRAMES verb main event arguments participants free modifiers circumstances (time, location,manner...) Mapping syntax to event frames Problem: secondary information (cause or antecedent of the main event) is ‘hidden’ in participial structures: [A befektetők által tegnap eladott részvények] megnövelték a tőzsde forgalmát. [The shares sold yesterday by the investors] increased the traffic at the stock exchange. Mapping syntax to event frames [A befektetők által tegnap eladott részvények] megnövelték a tőzsde forgalmát. [The shares sold yesterday by the investors] increased the traffic at the stock exchange. a befektetők / the investors / eladott / sold / tegnap / yesterday / részvények / shares / Mapping syntax to event frames [A befektetők által tegnap eladott részvények] megnövelték a tőzsde forgalmát. [The shares sold yesterday by the investors] increased the traffic at the stock exchange. A befektetők tegnap eladtak részvényeket. The investors sold shares yesterday. A solution a preprocessing module within the IE system which transforms participial structures into sentences with a finite predicate semantic frame matching may operate on transformed sentences 1st step: past participles within NPs • the participle preserves the meaning of its base verb • its arguments can be derived from the internal structure of the NP NPs in Hungarian 1. NPs in Hungarian 2. ADV NP+case DET Participles AP+case N+Postp V.INF ... (past, present) modifiers head Noun Participles in Hungarian ADJ – Participle homonimy is a problem: “mérsékelt PC-chip kereslet” modest /~moderated/ demand for PC-chips * Valaki mérsékelte a PC-chip keresletet. * Somebody moderated the demand for PC-chips “ragozott szóalakok” inflected word forms * Valaki ragozott szóalakokat. * Somebody inflected word forms. only participles can be transformed Participle or Adjective? syntactic tests comparative ADV formation predicative use impossibility of preverb detachment we need to decide in the context whether the given word form is an ADJ or a PART: 1. If at least one of the base verb’s complements is present, than it is a participle. Participle or Adjective? syntactic tests comparative ADV formation predicative use preverb detachment we need to decide in the context whether the given word form is an ADJ or a PART: 2. If at least one of the base verb’s complements / adjuntcs / a preverb is present, than it is a participle. Participle or Adjective? TESTS: • comparative: “mérsékeltebb kereslet” more moderate demand • predicative: “Ez a szóalak ragozott.” This word form is inflected. • ADV formation: mérsékelt mérsékelten moderate moderately • preverb detachment: “a [fel nem újított] házak” “the [re- not stored] houses” (=not restored) * Ezek a házak [fel nem újítottak]. * These houses are [re- not stored]. THE GRAMMAR - the correctness and informativity of the resulting sentence depends on the correct identification of verbal arguments and modifiers within the NP - then these elements are transformed according to their grammatical function • past participles may be formed from both transitive or intransitive verbs • if the base verb is intransitive, the head noun of the NP represents the subject of the base verb: “az összedőlt épület” /the collapsed building/ • if the base verb is transitive, the head noun represents the direct object of the base verb “a bejelentett változások” /the changes announced/ transitivity needs to be coded THE GRAMMAR transformation rules are (enhanced) FSTs: • they store relevant elements of the input NP in variables • the output is made up of the content of these variables but in an altered order + function words needed in the sentence • our delaf dictionary codes transitivity properties of verbs (on the basis of a lexicon-grammar of verbal argument structures) +- preverb feature shows whether the base verb has a preverb Transformation Graphs 1. Transitive Verbs transitive verbs without expressed subject (“somebody” insertion): Det (V_compl) Valaki V_vmib Det VMIB N –t N (V_compl) . transitive verbs with a subject with the PostP “által”: Det Nsubj Nsubj által V_vmib Det (V_compl) N –t VMIB (V_compl) . N Transformation Graphs 2. Intransitive Verbs head N becomes subject (patient) Det Det (V_compl) N V_vmib VMIB N (V_compl) . Structure of the graphs 1 graph 3 subgraphs according to complement-types: possessor / verbal complement+adjunct / nothing/ each subgraph divided into two paths: transitive / intransitive verbs Evaluation central aspect: to what extent does it augment the efficiency of the IE system? lack of information (recall value) is considered less important than incorrect information (precision) evaluated on the 231.000 words corpus of short business news; 1259 hits 898 qualified as informative precision: 64% further task: recall (requires a corpus with manually annotated participial structures) THANK YOU FOR YOUR ATTENTION! {gkata, eheja, magnes}@corpus.nytud.hu