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Syntactic Disambiguation through Lexicon Enrichment Second Stage Project Presentation Guide: Pushpak Bhattacharyya Ashish Almeida 03M05601 Overview • • • • • • • Motivation Problem definition Linguistic theory Lexical enrichment Design and implementation Results Future work May 23, 2017 2 Motivation • Robust and scalable UNL generation required • English analysis for extracting meaning • Correct analysis correct meaning representation • Identification of correct syntactic representation • Identification of correct semantic relation May 23, 2017 3 Preposition Phrase Attachment Problem • John covered the baby with a blanket. covered John the baby covered with a blanket John the baby with a blanket Verb attachment Noun attachment May 23, 2017 4 Universal Networking Language • He forwarded the mail to the minister. forward(icl>send) agt @ entry @ past gol obj He(icl>person) minister(icl>person) mail(icl>collection ) May 23, 2017 @def @def 5 Linguistic Insights • Syntactic level – Syntactic Frame – Subcategorization • Semantic level – Selectional restrictions – Thematic/theta roles May 23, 2017 6 Syntactic Frame • Sequence of words as they appear in sentences – [V-ART-N] … handed a book – [NP-to-NP] ... the mail to the minister – [V-NP-P-NP] … forwarded the mail to the minister May 23, 2017 7 Subcategorization • Verbs – He put the book on the table. – *He put the book. – *He put. • put: [ _NP PP-on] • Nouns – his reliance on/*at/*with her help. – *his reliance. • reliance: [ _PP-on] • Adjectives – He is fond of reading. • fond: [ _ PP-of] May 23, 2017 8 Selectional Restrictions • The boy murdered John. • *The boy murdered the tree. – Thus the verb ‘murder’ needs a human as object. • murder: [HUMAN _ HUMAN] May 23, 2017 9 Thematic Roles • Each argument of verb has a unique role associated with it. • Each role is assigned to a single argument. E.g. – The boy murdered John. • The boy • John - agent - patient/theme • Other thematic roles : Instrument, locative, goal • UNL relations: analogous to thematic roles. May 23, 2017 10 Lexicon Enrichment • Idiosyncratic information – Subcategorization – Thematic roles in terms of UNL relations • How to get this information ? – Subcategorization • Oxford advanced learner’s dictionary, WordNet – UNL relations • Beth Levin, manual effort May 23, 2017 11 An Example Dictionary Entry • forward • E.g. he forwarded the mail to the minister • [forward]{}“forward(icl>sent)” (VRB,VOA,VOA-PHSL, #_TO_A2,#_TO_A2_gol)<E,0,0>; headword Universal Word May 23, 2017 Attributes 12 Issues • The work focuses on – The [V-NP-P-NP] frame – Commonly used prepositions • In, on, of, with, from, to, for – Disambiguating to – Active voice May 23, 2017 13 Design • Fill the valency of the nearest element first. • If in the frame [V-N1-P-N2] – both V and N1 have #P in their subcategorization frames, then satisfy the demand of the nearest element to P, i.e., the noun first. • Else, give priority to that element which subcategorizes the preposition P • Else, give priority to the events and actions (can be verb or noun) – destroyV, destructionN etc. May 23, 2017 14 Summarization of Algorithm Conditions Action Attributes of Attributes of Attachment of Examples 1 #<P> #<P> _ N1 …paid a visit to the museum. 2 #<P> Not #<P> V ...passed the ball to Bill. …imposed heavy penalties on fuel dealers. 3 Not a #<P> Not #<P> 3 Not b #<P> Not #<P>, EVENT Attributes of V 5 Not #<P> NP1 #<P> May 23, 2017 NP2 _ NP2 PLACE V TIME …met him in his office. …met him in the afternoon. PLACE TIME N1 …cancelled a meeting with his friends. N1 …supplied plans for projects. 15 Problems with to • Infinitival to – Do not allow onion to brown • Preposition to – The lights changed from green to brown Problem: Detect if the lexical element is to-preposition or to-infinitive May 23, 2017 16 Heuristics to Detect to-preposition Criterion Preposition to - to is followed by a determiner - to is followed by a word followed by a plural marker - to is followed by an adjective - to is followed by a proper noun - to is followed by a pronoun - the matrix verb specifies that it needs a topreposition complement. - to is preceded by a noun which specifies that it needs a to-preposition complement. Infinitival to - the matrix verb specifies that it needs a toinfinitival complement. - to is preceded by a noun which specifies that it needs a to-infinitival complement. - to is followed by a base verb May 23, 2017 17 Implementation • Creating new dictionary with extra attributes • Writing new rules to use these new attributes – Rules to use subcategorization information – Rules for processing events (nouns and verbs) May 23, 2017 18 Analysis Engine (Enconverter) sentence Word1 Word2 Word3 Word4 LCW LAW RAW RCW … Wordn windows • Analysis windows – Left Analysis Window (LAW) – Right Analysis Window (RAW) • Condition windows – Many in number – LCWs, RCWs May 23, 2017 19 Operations in Analysis • • • • • Movement of heads Addition of two nodes Deletion of a node Creating relation between two nodes Adding dynamically inferred attributes to node May 23, 2017 20 Rules ; Right shift to affect noun attachment R{VRB,#_FOR_AR2:::}{N,#_FOR:::}(PRE,#FOR)P60; This states that IF The left analysis window is on a verb which takes a for-pp as the second argument (indicated by #_FOR_AR2) AND The right analysis window is on a noun which takes a for-pp as an argument (indicated by #_FOR) AND The preposition for follows the noun (indicated by (PRE,#FOR) ) THEN Shift right (indicated by R at the start of the rule) anticipating noun attachment for the PP. May 23, 2017 21 Other Rules ; Create relation between V and N2, after resolving the preposition preceding N2 <{VRB,#_FOR_AR2,#_FOR_AR2_rsn:::} {N,FORRES,PRERES::rsn:}P25; ;Delete the preposition ON >(VRB,EVENT,VOA){PRE,#ON:::} {N,UNIT,TIME,DAY:+ONRES,+PRERES::}P27; ;Create the relation tim between verb and noun <{VRB,VOA:::} {N,TIME,UNIT,ONRES,PRERES::tim:}P20; May 23, 2017 22 Testing • Resources: – British National Corpus – WordNet – Brown corpus • Filtered out – Phrasal verbs – Compound nouns – Longer sentences • Semantically different types of constructs tested in [V-N-P-N] frame. May 23, 2017 23 Cases of with Different semantic Roles in different syntactic and semantic environments Attachment Semantic relation Example Noun obj He cancelled [a meeting with his students]. Noun and She wore [a green skirt with a blouse]. Verb ins He [covered the baby with a blanket]. Verb gol That [provides him with a living]. Verb ptn He [is playing chess with his friend]. May 23, 2017 24 Results for of-preposition The results of testing for solving PP attachment and generating UNL Corpus Frames BNC WSJ V-N1-of-N2 V-N1-of-N2 May 23, 2017 Total no. of Sentences 1000 661 No. of Correct attachments & UNL relations Accuracy % 886 597 88 90 25 Conclusion • Lexical enrichment originating from key linguistic principles makes the analysis more correct • Rule-base design simplified due to distinction made between complements and adjuncts during analysis May 23, 2017 26 Future Work • Handling the alternation patterns of verbs • Applying the algorithm on all prepositions • Extracting the information through various resources – such as dictionaries and annotated corpus May 23, 2017 27 References • UNDL Foundation: The Universal Networking Language (UNL) specifications version 3.2. (2003) http://www.unlc.undl.org • Grimshaw, Jane.: Argument Structure. The MIT Press, Cambridge, Mass. (1990) • Brill, E. and Resnik, R.: A Rule based approach to Prepositional Phrase Attachment disambiguation. Proc. of the fifteenth International conference on computational linguistics. Kyoto. (1994) • Levin, Beth.: English verb Classes and Alternation. The University of Chicago Press, Chicago. (1993) • Hornby, A. S.: Oxford Advanced Learner’s Dictionary of Current English. Oxford University Press, Oxford.(2000) May 23, 2017 28 Thank you May 23, 2017 29 Example UNL In I deposited my money in my bank account. {unl} gol(deposit(icl>put):02.@entry.@past, account(icl>statement):0W) obj(deposit(icl>put):02.@entry.@past, money(icl>currency):0F) agt(deposit(icl>fasten):02.@entry.@past, I:0C) mod(money(icl>currency):0F, I:0C) mod(account(icl> statement):0W, bank(icl>possession):0R) mod(account(icl> statement):0W, I:0O) {/unl} May 23, 2017 30 Example UNL On I put the book on the table. {unl} gol(put(icl>move):02.@present.@entry, table(icl>object):0M.@def) obj(put(icl>move):02.@present.@entry, book(icl>publication):0A.@def) agt(put(icl>move):02.@present.@entry, I:00) {/unl} May 23, 2017 31 Example UNL To They served a wonderful meal to fifty delegates. {unl} gol(serve(icl>provide):05.@entry.@past, delegate(icl>person):12.@pl) obj(serve(icl>provide):05.@entry.@past, meal(icl>food):0O.@indef) agt(serve(icl>provide):05.@entry.@past, they(icl>thing):00) mod(meal(icl>food):0O.@indef, wonderful(mod<thing):0E) qua(delegate(icl>person):12.@pl, fifty(icl>number):0W) {/unl} May 23, 2017 32