Preposition Phrase Attachment in English Language Analysis Ashish Almeida 03M05601

PP attachment John read the report on new technologies. read John the PP attached to NP the report PP attached to VP * December 28, 2018 CFILT,IIT Bombay

Same Structure: different roles Ram ate rice with a spoon. -instrument ins(eat(icl>do).@past.@entry, spoon(icl>tool)) Ram ate rice with Sita. -co-agent cag(eat(icl>do).@past.@entry, Sita(iof>person)) December 28, 2018 CFILT,IIT Bombay

UNL and EnConvertor UNL is an intermediate language for representing meaning of natural language. EnConvertor is a language independent parser Rules are written for analysis UW Dictionary is created for analysis PP-attachment is handled in EnCo. December 28, 2018 CFILT,IIT Bombay

More about UNL UNL graph of John eats rice with a spoon eat(icl>do) ins spoon(icl>artifact) @ entry. @ present obj rice(icl>food) agt John(iof>person) December 28, 2018 CFILT,IIT Bombay

Adjuncts It provides extra information in a sentence. It attaches to the verb. Examples: Ram came home. Ram came home on Monday. Sita is sleeping. Sita is sleeping in the room. December 28, 2018 CFILT,IIT Bombay

Temporal Prepositional Phrases Represents temporal information with the help of an object e.g. on Sunday , for two days, at 5 p.m., on Diwali, in ice age, after the meeting, till 6 O’ clock, over two hours, beyond midnight Prepositions that can show temporality at over through before for since by in from during beyond till until to on after between inside into within of December 28, 2018 CFILT,IIT Bombay

Time attributes To identify the type of time word e.g. Attribute Examples TIME Today, March UNIT Day, second EVENT Morning, Dinner TIM_TOKEN am, pm SECOND* 12, 15 DAY* Sunday; 23 POFDAY Dinner, Sunset WEEK Week ZDIM Start, End, Middle December 28, 2018 CFILT,IIT Bombay

UNL of Temporal PPs Different UNL generation in two different cases Delete the preposition e.g. come at noon tim(come , noon) Retain the preposition e.g. come before noon tim(come, before) obj(before,noon) December 28, 2018 CFILT,IIT Bombay

Mapping from Prepositions to UNL relations Attributes of the Arguments at tim [TIME,TIM_TOKEN] in [N,TIME,MONTH] [N,TIME,YEAR] [N,POF_DAY] on [N,TIME,DAY] after tim-obj [N,TIME] [N,EVENT] before December 28, 2018 CFILT,IIT Bombay

Rules Rules for at-PP - Applies to “at 6 pm” ;delete at DL(VRB){PRE,#AT:::}{TIME,TIM_TOKEN: +ATRES,+PRERES,+pTIM::}P22; ;create relation tim <{VRB:::}{ATRES,PRERES,pTIM::tim:}P20; December 28, 2018 CFILT,IIT Bombay

Testing Wall Street Journal (WSJ) corpus is used. Sentences from Oxford advanced learner’s Dictionary are also tested. WSJ has V-N-P-N four-word sentence fragments All temporal cases are tested for correctness of UNL December 28, 2018 CFILT,IIT Bombay

Results #Total PPs 20801 #Temporal PPs 1326 #Cases of correct UNL 1112 Average accuracy 83.9 % Errors are mainly due to mistakes in corpus and inaccuracies in UW dictionary December 28, 2018 CFILT,IIT Bombay

Associative of-PP NP: the comedy of Shakespeare mod(comedy(icl>abstract thing), Shakespeare(iof >person)) NP: the eyes of the boy pof(boy(icl>person), eye(pof>body).@pl) AP: guilty of an offence obj(guilty(aoj>thing), offence(icl>abstract thing)) NP: book of Ram pos(book(icl>concrete thing), Ram(iof>person)) December 28, 2018 CFILT,IIT Bombay

Partitive of-PP e.g. that kind of people mod(people, kind) Here, in case of N1-OF-N2 the semantic head is the N2. The first NP indicates a quantity Examples cup of tea qua(tea, cup) bag of oranges bundle of sticks a pinch of salt Kind construction e.g. that kind of people mod(people, kind) Kind-type words : kind, type, sort, variety etc. December 28, 2018 CFILT,IIT Bombay

Argument structure (AS) Argument structure specify the structural frame into which a verb can be fitted. For example, *Ram saw. This is unacceptable as verb see has strict subcategorisation feature (+ _NP). That is verb see takes NP as object. Thus a valid sentence is Ram saw Sita. AS of see is (NP _ NP) December 28, 2018 CFILT,IIT Bombay

Adjunct and Complements He gave a book to Ram. give (NP _ NP to-PP) - without to Ram sentence is unacceptable - to Ram is complement He gave a book to Ram on Sunday - without on Sunday sentence is acceptable - on Sunday is adjunct Similarly, nouns and adjectives take complements December 28, 2018 CFILT,IIT Bombay

More on AS Ram accused Sita of cheating AS is (NP _ NP of-PP) UNL for the sentence frame with the verb accuse (agtNP _ objNP rsnof-PP) Whereas for adjuncts, the case relations differ. He saw the girl through the window. He saw the girl with anger. He saw the girl in the library. December 28, 2018 CFILT,IIT Bombay

Dictionary entry He gave a book to Ram. The lexicon will have entry of gave which provides AS information. [gave] {} “give(icl>do)” (VRB,VOA,VOA-PHSL, #_TO, #_TO_GOL,PAST) <E,0,0>; PP in the sentence can be identified as a complement or not. This solves the attachment in some cases. December 28, 2018 CFILT,IIT Bombay

Verb attachment of ‘of-PP’ Three possible cases V NP1 NP2 V attaches to NP2 NP2 attaches to NP1 (C) V NP1 NP2 V attaches to NP1 V attaches to NP2 (A) V NP1 NP2 V attaches to NP1 NP1 attaches to NP2 (B) December 28, 2018 CFILT,IIT Bombay

of-PP attachment cases ... remind him of Gita Case A ... saw the book of physics Case B ... drank a cup of milk Case C December 28, 2018 CFILT,IIT Bombay

Four cases of attachment Attachment in presence or absence of attribute of Attributes of V Attributes of NP1 Attachment of NP2 1 V,OF N,OF NP1 2 V,^OF 3 N,^OF V 4 December 28, 2018 CFILT,IIT Bombay

Rules ;Noun attachment R{VRB,#_OF:::}{N,#_OF:::}(PRE,#OF)P60; R{VRB,^#_OF:::}{N:::}(PRE,#OF)P60; ;Verb attachment, first resolve the immediate object <{VRB,#_OF,#_OF_OBJ:::}{N,^#_OF::obj:} (PRE,#OF)P30; December 28, 2018 CFILT,IIT Bombay

Testing process British National Corpus (BNC) is used. V-N-of-N type sentences are extracted from corpus. AS information is added to verbs and nouns using Oxford Advanced Learner’s Dictionary and Beth Levin’s verb classes. AS information is merged into the Dictionary. December 28, 2018 CFILT,IIT Bombay

Results Total Correct Incorrect V-attachment 7 N-attachment (all) 493 N-attachment (all) 493 439 54 Associative cases 411 362 49 Partitive cases 82 (16%) 77 5 500 446 December 28, 2018 CFILT,IIT Bombay

To sum up The PP attachment problem is successfully divided in two parts – complement PPs and adjunct PPs This division clearly delineates the problem so that their analysis does not conflict. Analysis of complements will be mostly driven by rich attribute set from lexicon Whereas analysis of adjuncts will be driven by rules December 28, 2018 CFILT,IIT Bombay

Contribution Deciding the overall strategy of analysis Providing computation insights in linguistic analysis Design of attribute set/introducing new attributes Design and implementation of rules for EnCo. Testing of sentences. Dictionary corrections/modifications December 28, 2018 CFILT,IIT Bombay

Future work Focus will be on complements. Also, that-clause, to and -ing infinite clause handling, PRO detection will be tried in similar fashion. Automatic/semi-automatic acquisition of AS information for dictionaries will be tried out. December 28, 2018 CFILT,IIT Bombay