CSCI 587 - Lecture 11 NLP in Prolog

• Parsing with Transition Networks
• Equivalence of RTNs/CFGs
• Finding equivalent grammar for RTNs
• Finding equivalent RTN for grammars
• Regular expressions: recursive definition
  • Base case: If a is in the alphabet then a is a regular expression and it matches "a".
  • Recursive cases: if r₁ and r₂ are regular expressions then
    1. r₁r₂ is a regular expression
    2. r₁ | r₂ is a regular expression
    3. r₁ * is a regular expression
    4. ( r₁ ) is a regular expression
• Regular Expression Describing Language <--> Recognizable by DFA
• Example: 010*(10 | 11)
• The Chomsky Hierarchy Box 3.1
  • regular grammars
  • context sensitive
  • unrestricted
• DFA <--> Left Regular Grammar
• NLP in Prolog: nlp, nlp2

  s(X):- np(X, Y), vp(Y, []).
  np(X, Y):- det(X, Z), noun(Z, Y).
  vp(X, Y):- verb(X, Z), np(Z, Y).
  noun([A|X],X) :- cat(noun, A).
  verb([A|X],X) :- cat(verb, A).
  det([A|X],X) :- cat(det, A).
  
  cat(noun,boy).
  cat(noun,frog).
  cat(noun,girl).
  cat(verb,likes).
  cat(verb,hates).
  cat(det,the).
  cat(det,a).
  

• np(X,Y) means there is a noun phrase at the front of the list X and the remainder of the input after the noun phrase is Y
• Dictionary lookup for lexical items
• ?-s([ the, boy, likes, the, girl]).
• Prolog Traces: appendScript, nlp2Script
  • CALL
  • EXIT
  • REDO
  • FAIL

Readings

Sections 3.8

Prolog examples in /class/csci587/Prolog : family, nlp, nlp2

Chapter 1 of Programming in Prolog by Clocksin and Mellish.

Reading Room Sumwalt 203