Download Semantics I: General framework I

CS 544: Lecture 3.1
Problems in Discourse
Jerry R. Hobbs
USC/ISI
Marina del Rey, CA
Outline of Next 6 Lectures
1. Interpretation problems in discourse:
A typology of sorts
2. Interpretation problems in discourse:
Examples in the target texts
3. All of syntax and compositional semantics
4. Interpretation as abduction and local pragmatics
problems; MiniTacitus
5. Discourse coherence
6. Linking with known theory or set of interests
Is There Systematicity?
The basic unit of information is the predication:
p(x,y)
What is p?
predicate
strengthening
What are x and y?
coreference
What’s the relation between p and x, p and y?
In what way is it appropriate for p to describe x? y?
metonymy, metaphor, ...
p(x,y) & q(y,z)
What’s the relation between these two predications?
intraclausal coherence, discourse coherence
(predicate strengthening on sentence adjacency)
What is the Predicate?
Interpreting compound nominals:
feeder texts => feeder(x,y) & nn(y,z) & text(z)
Harvard protocircuitry, chocolaty mess, face value
Interpreting possessives:
its predecessors’ trainings, my texts, H’s simple-mindedness
Interpreting “of”:
paraphrase of text: predicate-argument relation
Interpreting other prepositions:
organizing in upheavals, sense from the insensate
Interpreting other underspecified predicates:
acquire facts, got a reading
Text gives us general predicates that we understand specifically.
What is the Argument?
Coreference
Pronouns:
H .... It ....; I .... We ....; Lentz .... He ....; ... itself ...
English was a mess, it began to dawn on me.
Definite noun phrases:
Anaphoric: <conflict in previous 173 pages> .... the problem
Determinative: the knowledge H had inherited
Even indefinite noun phrases:
diagramming tasks.... a simple story ....
rule-based .... “facts” .....
Implicit arguments:
Native speakers (of English)
Why this Predicate with this
Argument?
p(x) interpreted as q(x)
where p(x) --> q(x)
Finding relevant aspect of predicate:
hideous diagramming tasks;
knowledges: setOf(knowledge)
Metaphor interpretation:
wringing sense out of insensate; ..., it began to dawn on me
English was a chocolaty mess; shattered visage of English
Metonymy interpretation:
“The missionary ...” produced ... alternatives.
protocircuitry missed; story keeps H paraphrasing
p(x) interpreted as p(f(x))
Clause-Internal Coherence
Relations that go beyond the predicate-argument relations
conveyed by syntactic structure:
my ... feeder texts:
my = I give H text; feeder: I feed H text so H will grow
crude but increasingly specific: contrast
index, access and arrange: similar computational operations
inherited from predecessors’ trainings:
predecessor defeasibly implies inherit
Discourse Coherence
Relations between successive segments of discourse are typically
varieties of
rephrasing/elaboration:
H was learning. Organizing itself in upheavals.
similarity and contrast, generalization and examplification:
How to index ... remained the problem. But H was learning.
Paragraphs 3 and 4: General. Specific. Specific.
background (figure-ground):
successive changes of state, occasion:
... it dawned on me. I wondered ...
causality, enablement, violated causality or implication:
... wasn’t rule-based. We could not estimate how many “facts”...
We could not estimate.... But ... insights.
Situating Text w.r.t.
a Background Theory
Often an important part of understanding a text is anchoring it
in a background theory, e.g. Chapter 3 in Chapter 2 of a textbook.
In this text, much depends on anchoring examples in a background
theory of parsing and ambiguity:
“The missionary was prepared to serve.”
“Time flies like an arrow.”
“Help set implied precedents in sentences with ambiguous parts.”
“The trainer talked to the machine in the office with a terminal.”
Aim of this Part of Course
To learn to recognize these problems
and to get some idea about how they
might be approached.