Presentation is loading. Please wait.

Presentation is loading. Please wait.

LING 581: Advanced Computational Linguistics Lecture Notes January 30th.

Similar presentations


Presentation on theme: "LING 581: Advanced Computational Linguistics Lecture Notes January 30th."— Presentation transcript:

1 LING 581: Advanced Computational Linguistics Lecture Notes January 30th

2 Relative clause constructions Terminology – gap (__): indicates where the head of the construction is interpreted – Subject RC: the man (that|who) __ saw me – Object RC: the man (that|who) I saw __ – Subject and object RCs can appear in subject and object positions freely: The man that saw me left the room The man that I saw left the room I saw the man that saw me I again saw the man that I saw Note: the relative pronoun is the that/who/which

3 Relative clause constructions Terminology contd.: – Infinitival/untensed vs. tensed John saw Mary(tensed) John sees Mary(tensed) John to see Mary (untensed) – In RC constructions: the man to see Mary a person to see a time to go see Mary Note: subject is always missing… But its not always the RC gap Note: subject is always missing… But its not always the RC gap

4 Relative clause constructions Terminology contd.: – Zero refers to a missing relative pronoun – Zero RCs: the man I saw(tensed) the man to see(untensed) – *Zero: *the man saw me / the man who saw me *the man was seen by me / the man who was seen by me The horse raced past the barn fell – must be zero: *a person that to see *the man that to see Mary

5 Homework Exercise SubjectNon-Subject Tensed relatives Untensed relatives Frequency counts thatwhich/who/what/when/ where zero Tensed relatives

6 Homework Exercise Review Use tregex to search for relative clauses as defined in Parsing Guidelines section 4.2.2: 2.zero relative clauses

7 Homework Exercise Review Use tregex to search for relative clauses as defined in Parsing Guidelines section 4.2.2: 2.zero relative clauses

8 Homework Exercise Review Use tregex to search for relative clauses as defined in Parsing Guidelines section 4.2.2: 3.infinitival relative clauses

9 Homework Exercise Review Use tregex to search for relative clauses as defined in Parsing Guidelines section 4.2.2: 3.infinitival relative clauses

10 Homework Exercise Review Use tregex to search for relative clauses as defined in Parsing Guidelines section 4.2.2: 3.infinitival relative clauses

11 Homework Exercise Review From page 17:

12 Homework Exercise Review Use tregex to search for relative clauses as defined in Bracketing Guidelines (prsguid1.pdf) section 4.2.2: 1.wh- and that- relative clauses Two subtypes: WHNP NP-trace WHADVP ADVP-trace Two subtypes: WHNP NP-trace WHADVP ADVP-trace Note: the format in the guide doesnt always match exactly with WSJ trees … -NONE-

13 Homework Exercise Review Use tregex to search for relative clauses as defined in Bracketing Guidelines (prsguid1.pdf) section 4.2.2: 1.wh- and that- relative clauses MatchesPattern < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) << < (/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i))) MatchesPattern < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) << < (/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i)))

14 Homework Exercise Review Browsing through the matches and refining the search is always a good idea … to see what we have inadvertently picked up or have not thought of

15 Homework Exercise Review Note: 2 nd matching tree has an intervening PP:

16 Homework Exercise Review Note: 5 th matching tree has an intervening PP: Note: intervening punctuation is also common The plant, which is owned by Hollingsworth & Vose Co., was under contract … Note: intervening punctuation is also common The plant, which is owned by Hollingsworth & Vose Co., was under contract …

17 Homework Exercise Review < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) Note: the SBAR from NP-SBJ was extraposed to the VP Note: the SBAR from NP-SBJ was extraposed to the VP Note: *ICH* non-subject relative clause Note: *ICH* non-subject relative clause

18 Homework Exercise Review < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) This is NOT a relative clause construction! This is NOT a relative clause construction!

19 Homework Exercise Review < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) The relative clause gap here is ADVP Infinitival/non-tensed clause

20 Homework Exercise Review < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) *ICH* subject relative clause Note: the SBAR from the NP object was right extraposed to the VP Note: the SBAR from the NP object was right extraposed to the VP

21 Homework Exercise Review < NP < SBAR < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) Coordination SBAR SBAR CC SBAR Coordination SBAR SBAR CC SBAR

22 Homework Exercise Review < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) < NP < (SBAR < /^WH(NP|ADVP)-([0- 9]+)$/#2%i) Excludes *ICH* cases Excludes coordination …

23 Homework Exercise Review < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i) < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i << (/^(NP|ADVP)/ < (/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i)))

24 Homework Exercise Review < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i << (NP- SBJ < /^-NONE-$/)) < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i << (NP- SBJ < (/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i)))

25 Homework Exercise Review Lets look at the *ICH* subcases:

26 Homework Exercise Review < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/))

27 Homework Exercise Review < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/)) This is NOT a relative clause construction! This is NOT a relative clause construction!

28 Homework Exercise Review < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/)) < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : /^SBAR-([0- 9]+)$/#1%i Only 1 out of the 4 is NOT a relative clause construction! Only 1 out of the 4 is NOT a relative clause construction!

29 Homework Exercise Review < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/)) < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : /^SBAR-([0- 9]+)$/#1%i Search string is too restrictive: SBAR-PRP SBAR-NOM Search string is too restrictive: SBAR-PRP SBAR-NOM

30 Homework Exercise Review < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : (/^SBAR.*-([0-9]+)$/#1%i < /^WH(NP|ADVP)-([0-9]+)$/) < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : (/^SBAR.*-([0-9]+)$/#1%i < /^WH(NP|ADVP)-([0-9]+)$/#2%j << /\*T\*-([0- 9]+)/#1%j) Not a trace? BUG? Not a trace? BUG?

31 Relevance of Treebanks Statistical parsers typically construct syntactic phrase structure – theyre trained on Treebank corpora like the Penn Treebank Note: some use dependency graphs, not trees

32 Parsers trained on the Treebank Dont recover fully-annotated trees – not trained using nodes with indices or empty (-NONE-) nodes – not trained using functional tags, e.g. –SBJ Therefore they dont fully parse Example: no SBAR node in … a movie to see Stanford parser

33 Parsers trained on the Treebank SBAR can be forced by the presence of an overt relative pronoun, but note there is no subject gap:

34 Parsers trained on the Treebank Probabilities are estimated from frequency information of each node given surrounding context (e.g. parent node, or the word that heads the node) Still these systems have enormous problems with prepositional phrase (PP) attachment Example: (borrowed from Igor Malioutov) – A boy with a telescope kissed Mary on the lips – Mary was kissed by a boy with a telescope on the lips PP with a telescope should adjoin to the noun phrase (NP) a boy PP on the lips should adjoin to the verb phrase (VP) headed by kiss

35 Active/passive sentences Examples using the Stanford Parser: Both active and passive sentences are parsed incorrectly Both active and passive sentences are parsed incorrectly

36 Active/passive sentences Examples: X on the lips modifies Mary X on the lips modifies telescope

37 Homework Exercise Use tregex to find out how many passive sentences there are in the Treebank WSJ section? The passive construction (according to the Bracketing Guidelines) – Note: by-phrase containing logical subject (LGS) is optional


Download ppt "LING 581: Advanced Computational Linguistics Lecture Notes January 30th."

Similar presentations


Ads by Google