Information Extraction: Relations, Events, and Time

21.5 Representing aspect

1. What is aspect (Aktionsart)?
   The categorization of events by their internal temporal structure: whether ongoing or ended, happening at a point or over an interval.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 21, §21.5, p. 488
2. What is the most basic aspectual distinction?
   Events, which involve change, versus states, which don’t: a participant being in a state or having a property, seen as unchanging (“I need the cheapest fare”).
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 21, §21.5, p. 488
3. What are Vendler’s four aspectual classes?

   class	example	properties
   stative	I know my departure gate.	no change
   activity	John is flying.	over time, no endpoint
   accomplishment	Sally booked her flight.	over time, natural endpoint (telic)
   achievement	She found her gate.	punctual, results in a state

   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 21, §21.5, p. 488
4. What does telic mean?
   From Greek telos “end, goal”: events conceptualized as having a natural endpoint or goal, as accomplishments and achievements are.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 21, §21.5, p. 488
5. How do accomplishments differ from achievements?
   Both result in a state, but accomplishments unfold over time toward the end (“booked me a reservation”), while achievements are punctual, with no conceptualized lead-up process (“she found her gate”, “we reached New York”).
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 21, §21.5, pp. 488–489
6. Is an event’s aspectual class determined by its verb?
   No: “I flew” is an activity, while “I flew to New York” is an accomplishment; the class depends on the whole expression in context.
   • Jurafsky & Martin, Speech and Language Processing, 3rd ed. draft, ch. 21, §21.5, p. 489