Semantic Role Labeling

Introduction

1. What were Pāṇini’s kārakas?
   In his Sanskrit grammar (7th–4th c. BCE), rules describing semantic relationships between a verb and its noun arguments (agent, instrument, destination…): the earliest known model of how events and their participants are realized linguistically.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 22, Introduction, p. 499
2. What central question do semantic roles help answer?
   “Who did what to whom” (and perhaps when and where): how participants relate to events.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 22, Introduction, p. 499
3. Why are semantic roles needed to understand “XYZ corporation bought the stock” vs “They sold the stock to XYZ corporation” vs “the stock purchase by XYZ corporation”?
   The same purchase event and the same buyer appear with different verbs or nouns and in different syntactic positions (subject, indirect object, by-phrase, compound); semantic roles capture the shared shallow meaning: XYZ Corp is the buyer, the stock the thing bought.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 22, Introduction, p. 499
4. What are selectional restrictions?
   Preferences a predicate expresses about its arguments, e.g. that the theme of eat is generally something edible.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 22, Introduction, p. 499