Linguistics 239E: Grammar Engineering

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Linguistics 239E Grammar Engineering

• Ron Kaplan and Tracy King

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Administrivia

• Schedule Course, Office hours?
• Requirements
• Overview

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Applications of Language Engineering
Shallow
Synthesis
Broad
Domain Coverage
Narrow
Deep
Low
High
Functionality
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Grammar engineering for deep processing

• Draws on theoretical linguistics, software
  engineering
• Theoretical linguistics gt papers
• Generalizations, universality, idealization
  (competence)
• Software engineering gt programs
• Coverage, interface, QA, maintainability,
  efficiency, practicality
• Grammar engineering
• GrammarTheory ProgramProgramming language
• Reflect linguistic generalizations
• Respect special cases of ordinary language
• Deal with large-scale interactions
• Theory/practice trade-offs

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Deep analysis matters if you care about
the answer

• Example
• A delegation led by Vice President Philips, head
  of the chemical division, flew to Chicago a
  week after the incident.
• Question Who flew to Chicago?
• Candidate answers
• division closest noun
• head next closest
• V.P. Philips next

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Why deep analysis is difficult

• Languages are hard to describe
• Meaning depends on complex properties of words
  and sequences
• Different languages rely on different properties
• Errors and disfluencies

• Languages are hard to compute
• Expensive to recognize complex patterns
• Sentences are ambiguous
• Ambiguities multiply explosion in time and
  space

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Different patterns code same meaning
The small children are chasing the dog.
English Group, order
Japanese Group, mark
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Different patterns code same meaning
The small children are chasing the dog.
LFG theory minor adjustments on universal theme
English Group, order
Japanese Group, mark
Chase(small(children), dog)
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LFG architecture
Modularity

• C-structures and f-structures in piecewise
  correspondence.

S
f
NP
VP
John
V
NP
likes
Mary
Formal encoding of grammatical relations
Formal encoding of order and grouping
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LFG grammar
Rules
Lexical entries
S ? NP VP (? SUBJ)? ??
John (? PRED)John (? NUM)SG likes (?
PRED)likeltSUBJ, OBJgt (? SUBJ NUM)SG
VP ? V NP ?? (? OBJ)?

• Context-free rules define valid c-structures
  (trees).
• Annotations are instantiated at tree nodes to
  give equational constraints that corresponding
  f-structures must satisfy.
• Satisfiability of constraints determines
  grammaticality.
• F-structure is solution for equations (if
  satisfied).

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Rules as well-formedness conditions
S
SUBJ
NP
VP
A tree containing S over NP - VP is OK if
F-unit corresponding to NP node is SUBJ of f-unit
corresponding to S node The same f-unit
corresponds to both S and VP nodes.
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Inconsistent equations Ungrammatical

• Whats wrong with They walks ?

f v and (v SUBJ NUM)SG gt (f SUBJ
NUM)SG
If a valid inference chain yields FALSE, the
premises are unsatisfiable.
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