LING 581: Advanced Computational Linguistics Lecture Notes April 20th.
LING 581: Advanced Computational Linguistics Lecture Notes January 30th.
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Transcript of LING 581: Advanced Computational Linguistics Lecture Notes January 30th.
![Page 1: LING 581: Advanced Computational Linguistics Lecture Notes January 30th.](https://reader036.fdocuments.net/reader036/viewer/2022062417/5519aa57550346e40d8b46ca/html5/thumbnails/1.jpg)
LING 581: Advanced Computational Linguistics
Lecture NotesJanuary 30th
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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 sawNote: the relative pronoun is the that/who/which
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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 it’s not always the RC gap
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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
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Homework Exercise
Subject Non-Subject
Tensed relatives
Untensed relatives
Frequency counts
that which/who/what/when/where
zero
Tensed relatives
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Homework Exercise Review• Use tregex to search for relative clauses as defined in Parsing
Guidelines section 4.2.2:2. zero relative clauses
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Homework Exercise Review• Use tregex to search for relative clauses as defined in Parsing
Guidelines section 4.2.2:2. zero relative clauses
![Page 8: LING 581: Advanced Computational Linguistics Lecture Notes January 30th.](https://reader036.fdocuments.net/reader036/viewer/2022062417/5519aa57550346e40d8b46ca/html5/thumbnails/8.jpg)
Homework Exercise Review• Use tregex to search for relative clauses as defined in Parsing
Guidelines section 4.2.2:3. infinitival relative clauses
![Page 9: LING 581: Advanced Computational Linguistics Lecture Notes January 30th.](https://reader036.fdocuments.net/reader036/viewer/2022062417/5519aa57550346e40d8b46ca/html5/thumbnails/9.jpg)
Homework Exercise Review• Use tregex to search for relative clauses as defined in Parsing
Guidelines section 4.2.2:3. infinitival relative clauses
![Page 10: LING 581: Advanced Computational Linguistics Lecture Notes January 30th.](https://reader036.fdocuments.net/reader036/viewer/2022062417/5519aa57550346e40d8b46ca/html5/thumbnails/10.jpg)
Homework Exercise Review• Use tregex to search for relative clauses as defined in Parsing
Guidelines section 4.2.2:3. infinitival relative clauses
![Page 11: LING 581: Advanced Computational Linguistics Lecture Notes January 30th.](https://reader036.fdocuments.net/reader036/viewer/2022062417/5519aa57550346e40d8b46ca/html5/thumbnails/11.jpg)
Homework Exercise Review
• From page 17:
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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-traceWHADVP ADVP-trace
Note: the format in the guide doesn’t always match exactly with WSJ trees … -NONE-
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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
Matches Pattern11598 @NP < NP < SBAR 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i) << (@NP < (/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i)))
1. 2.
3.
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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
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Homework Exercise Review
• Note: 2nd matching tree has an intervening PP:
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Homework Exercise Review
• Note: 5th matching tree has an intervening PP:
Note: intervening punctuation is also commonThe plant, which is owned by Hollingsworth & Vose Co., was under contract …
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Homework Exercise Review
11598@NP < NP < SBAR 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)
Note: the SBAR from NP-SBJ was extraposed to the VP
Note: *ICH* non-subject relative clause
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Homework Exercise Review
11598@NP < NP < SBAR 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)
This is NOT a relative clauseconstruction!
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Homework Exercise Review
11598@NP < NP < SBAR 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)
The relative clause gap here is ADVP
Infinitival/non-tensed clause
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Homework Exercise Review
11598@NP < NP < SBAR 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)
*ICH* subject relative clause
Note: the SBAR from the NP objectwas right extraposed to the VP
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Homework Exercise Review
11598@NP < NP < SBAR 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)
CoordinationSBAR SBAR CC SBAR
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Homework Exercise Review
• 9028 @NP < NP < (SBAR < /^WHNP-([0-9]+)$/#1%i)• 10290 @NP < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)
$/#2%i)
• Excludes *ICH* cases• Excludes coordination …
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Homework Exercise Review
• 10290 @NP < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i)• 10326 @NP < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i
<< (/^(NP|ADVP)/ < (/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i)))
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Homework Exercise Review• 8575 @NP < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i << (NP-SBJ
< /^-NONE-$/))• 5975 @NP < NP < (SBAR < /^WH(NP|ADVP)-([0-9]+)$/#2%i << (NP-SBJ <
(/^-NONE-$/ < /^\*T\*-([0-9]+)$/#1%i)))
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Homework Exercise Review
Let’s look at the *ICH* subcases:
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Homework Exercise Review
159 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/))
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Homework Exercise Review
159 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/))
This is NOT a relative clauseconstruction!
![Page 28: LING 581: Advanced Computational Linguistics Lecture Notes January 30th.](https://reader036.fdocuments.net/reader036/viewer/2022062417/5519aa57550346e40d8b46ca/html5/thumbnails/28.jpg)
Homework Exercise Review159 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/))155 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : /^SBAR-([0-9]+)$/#1%i
Only 1 out of the 4 is NOT a relative clauseconstruction!
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Homework Exercise Review159 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*/))155 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : /^SBAR-([0-9]+)$/#1%i
Search string is too restrictive:SBAR-PRPSBAR-NOM
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Homework Exercise Review• 116 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*ICH\*-([0-9]+)/#1%i)) : (/^SBAR.*-
([0-9]+)$/#1%i < /^WH(NP|ADVP)-([0-9]+)$/)• 115 @NP < NP < (SBAR < (/^-NONE-$/ < /^\*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?
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Relevance of Treebanks
• Statistical parsers typically construct syntactic phrase structure– they’re trained on Treebank corpora like the Penn
Treebank• Note: some use dependency graphs, not trees
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Parsers trained on the Treebank
• Don’t recover fully-annotated trees– not trained using nodes with indices or empty (-NONE-) nodes– not trained using functional tags, e.g. –SBJ
• Therefore they don’t fully parse• Example: no SBAR node in … a movie to see
Stanford parser
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Parsers trained on the Treebank
• SBAR can be forced by the presence of an overt relative pronoun, but note there is no subject gap:
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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
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Active/passive sentences
• Examples using the Stanford Parser:
Both active and passivesentences are parsed incorrectly
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Active/passive sentences
• Examples:
X on the lips modifies MaryX on the lips modifies telescope
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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