Using World Knowledge

Reference: Chapter 15 of Allen
Aim:
This section considers the problem of using world knowledge in interpreting logical forms.
Keywords: coherence, reference, disambiguation, implicature, expectations, matching, scripts
Plan:
  • establishing coherence
  • matching against expectations
  • using scripts

Coherence

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via Google images.


Coherence 2

Footnotes:
[1] ignite comes from the Latin word ignis = fire
[2] illuminate comes from the Latin word lumen = light


Coherence 3


Matching Against Expectations


Matching Against Expectations 2


Matching Against Expectations 3


Matching Against Expectations 4


Matching Against Expectations 5

semantic net diagrams

Figure 15.1 from Allen
The expectation and two possible interpretations


Matching Against Expectations 6

result of matching semantic nets

Figure 15.2 from Allen
The result of matching/unifying E1 and E2


Matching Against Expectations 7

Or, in Prolog terms:

event(e1_2).
isa(e1_2, ignite).
agent(e1_2, jack1).
instrument(e1_2, match33).
theme(e1_2, candle1).


Scripts: Understanding Stereotypical Situations


Scripts: Understanding Stereotypical Situations 2

Example of (generic) script:

Roles Actor, Clerk, SourceStation, DestStation, Train, Booth, Ticket, Money
Constraints Person(Actor), Person(Clerk), Station(SourceStation), Station(DestStation), TicketBooth(Booth), In(Booth, SourceStation), At(Clerk, Booth), TicketFor(Ticket, SourceStation, DestStation), Value(Money, PriceOf(Ticket))
Preconditions Owns(Actor, Money), At(Actor, SourceStation)
Effects ¬ Owns(Actor, Money), ¬ At(Actor, SourceStation), At(Actor, DestStation),
Decomposition PurchaseTicket(Actor, Clerk, Ticket, SourceStation)
Goto(Actor, Location(Train))
GetOn(Actor, Train)
Travel(Train, SourceStation, DestStation)
Arrive(Train, DestStation)
GetOff(Actor, Train)

Scripts 3


Scripts 4


Scripts 5


Summary

Using World Knowledge

We have looked at the problem of establishing coherence in a discourse, and the fact that doing so may involve eliminating unlikely readings of the sentences in the discourse. We saw that unification/matching can be helpful in this process.

We have also looked at scripts, that is, frames that describe sequences of events in stereotyped/common situations, as a mechanism for dealing with longer discourses.


© Copyright Bill Wilson, 2007, except where another source is acknowledged. The material in this section is adapted from James Allen's book "Natural Language Processing".
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