1. LING/C SC 581: Advanced Computational Linguistics
Lecture 20
March 28th

2. Administrivia
Homework 8 on tregex

3. tregex
The best introduction to Tregex is the brief powerpoint tutorial for Tregex by Galen Andrew.
Google: wonderful world of tregex
The_Wonderful_World_of_Tregex.ppt

4. tregex Preferences

5. tregex
useful command line tool:
diff <file1> <file2>

6. tregex

7. tregex Help: tregex expression syntax is non-standard wrt bracketing
S < VP
S < NP

8. tregex
Help: tregex boolean syntax is also non-standard

9. tregex
Help

10. tregex x <, y, 1st child y; x <- y, last child y;
x $+ y, x immediate left sister of y

11. tregex
same node
Pattern:
<, $+ (/,/ $+ $+ /,/=comma))) <- =comma)
Key:
<, first child
$+ immediate left sister
<- last child

12. tregex
Help

13. tregex

14. tregex Different results from:
@SBAR < /^WH.*-([0-9]+)$/#1%index << < (/^-NONE-/ < /^\*T\*-([0- 9]+)$/#1%index))

15. tregex Reason for difference Example:
WHADVP also possible (not just WHNP)

16. Treebank Guide Parsing guide 1, prsguid1.pdf (318 pages):
prsguid2.pdf: addendum for the Switchboard corpus

17. Homework 8 Read about *PPA* in prsguid1.pdf (section 5.2).
Q1: Write a tregex expression to search for Prepositional Phrase (PP) PPAs. How many of them are there?

18. Homework 8
Q2: Write a tregex expression to search for non-PP PPAs. I.e. what other basic categories of PPAs besides Prepositional Phrase (PP) PPAs are there? List them.
Note: by basic we

19. Homework 8 Q3: Find the section on Topicalization in prsguid1.pdf.
How are topicalized elements marked?
How many examples of topicalized elements are there in the WSJ?
Using Save Matched Sentences and any necessary Python code, how many types of topicalized elements are there?
How many types occur more than once? (You may want to use nltk.FreqDist().)
Note: by type we mean by grammatical category

20. Homework 8
Due next Wednesday night.
Review next week this time.