Worksheet: A Hard NLP Structured Annotation Task

Event Causal Relation Extraction
Course: Natural Language Annotation for Machine Learning Task Type: Structured annotation (event detection + causal relations)
Objective: Understand why structured annotation is harder than sequence labeling
Author: Jin Zhao

Background

You are annotating data for an AI system that extracts causal relations between events from news text.

A causal relation means that: One event (CAUSE) brings about or contributes to another event (EFFECT)

This task requires:

Event Definition (for this worksheet)

An event is a real-world occurrence or action described in the text (e.g., attack, protest, collapse, evacuation, shutdown).

Causal Relation Labels

CAUSES — Event A directly causes Event B
ENABLED — Event A made Event B possible but did not directly cause it
NO-RELATION — No causal relation is expressed
UNCERTAIN — Causality is suggested but not clearly stated

Part 1: Warm-up — What Counts as Causation?

Question 1

Which of the following words or phrases often signal causality? (Check all that apply.)

Part 2: Explicit Causation (Easier Case)

Sentence 1
"Heavy rainfall caused flooding across the region."
Event A: heavy rainfall   |   Event B: flooding
Question 2

What is the relation between Event A and Event B?

Part 3: Temporal ≠ Causal (Classic Trap)

Sentence 2
"Flooding occurred after heavy rainfall in the region."
Event A: heavy rainfall   |   Event B: flooding
Question 3

Is this sentence explicitly causal?

Part 4: Implicit Causality (Harder Case)

Sentence 3
"The bridge collapsed, leaving dozens stranded."
Event A: bridge collapsed   |   Event B: people stranded
Question 4

Is Event A causally related to Event B?

Part 5: Multi-Event Causal Chains

Sentence 4
"An explosion damaged the power station, causing widespread outages and forcing evacuations."
Event A: explosion   |   Event B: power station damaged   |   Event C: power outages   |   Event D: evacuations
Question 5

Which causal relations should be annotated? (Check all that apply.)

Part 6: Negation and Counterfactuals

Sentence 5
"The evacuation was avoided because the fire was quickly contained."
Event A: fire contained   |   Event B: evacuation
Question 6

How should this be annotated?

Part 7: Speculation and Modality

Sentence 6
"Officials said the strike may have triggered the supply shortage."
Question 7

How confident is the causal claim?

What label would you assign?

Part 8: World Knowledge vs Text Evidence

Sentence 7
"The hurricane hit the coast. Thousands of homes were destroyed."
Question 8

Should you annotate a causal relation?

Part 9: Group Discussion

Discuss with your group.

Question 9

Where did you disagree most?

Part 10: Annotation Design Decisions

Question 10

Which guideline would most reduce disagreement?

Part 11: Modeling Consequences (ML Perspective)

Question 11

If annotators disagree on causality, what might a model trained on this data learn?

Final Reflection

Question 12

Why is causal relation extraction harder than event detection alone?

Key Takeaway (for class discussion)

  • Causality is not directly observable in text—it is inferred, interpreted, and often underspecified.
  • Structured annotation tasks encode theories about the world, not just labels.
One-sentence takeaway: In structured annotation, you are modeling relationships between interpretations, not just words.