Worksheet: Temporal Expression Annotation

Understanding time in text: dates, durations, and temporal relations
Course: Natural Language Annotation for Machine Learning Task Type: Span labeling + Normalization + Relation extraction
Author: Jin Zhao

Background

Temporal annotation involves identifying time expressions (TIMEX) in text, normalizing them to standard formats, and annotating temporal relations between events.

TIMEX (Temporal Expression): A word or phrase that refers to a point in time, duration, or frequency.

Temporal Relation: How two events or times relate (before, after, during, etc.).

Types of Temporal Expressions

TypeDescriptionExample
DATECalendar date or period"January 15, 2024", "last week"
TIMETime of day"3:30 PM", "noon"
DURATIONLength of time"two hours", "for months"
SETRecurring time"every Tuesday", "annually"

Part 1: Identifying Temporal Expressions

The meeting scheduled for [next Monday] has been postponed. We will reconvene [in two weeks], specifically on [February 12th]. The original [three-hour] session will be shortened to [90 minutes].

Question 1

Classify each highlighted expression:

ExpressionType
"next Monday"
"in two weeks"
"February 12th"
"three-hour"
"90 minutes"

Part 2: Normalization

Temporal expressions must be normalized to a standard format (ISO 8601) for processing.

Document Creation Time (DCT): The reference point for relative expressions. Assume DCT = 2024-01-29 for this worksheet.

Question 2

Normalize these expressions (DCT = January 29, 2024, Monday):

ExpressionNormalized Value
"yesterday"
"next Friday"
"last summer"
"three days ago"
"the 90s"

Part 3: Ambiguous Expressions

"The project started [in March] and was completed [six months later]."

Question 3

What year does "in March" refer to? (DCT = January 29, 2024)

Part 4: Temporal Relations

Events and times can be related temporally. Common relations include:

RelationMeaningExample
BEFOREA ends before B starts"He left before she arrived"
AFTERA starts after B ends"She arrived after he left"
DURINGA occurs within B's span"It rained during the game"
OVERLAPA and B share some time"While cooking, I listened to music"
SIMULTANEOUSA and B at same time"The explosion and flash were simultaneous"

"[John arrived] at the office at [9 AM]. [The meeting started] at [10 AM]. [He was still preparing] when [the CEO walked in]."

Question 4

Identify the temporal relations:

Event AEvent BRelation
John arrived Meeting started
He was preparing CEO walked in

Part 5: Complex Temporal Reasoning

"The company was founded [two decades before] the CEO was born. She joined the firm [in her twenties] and became CEO [after 15 years]. [Last year], the company celebrated its [50th anniversary]."

Question 5

Can you determine when the company was founded? (DCT = 2024)

How old is the CEO approximately?

Part 6: Annotate This Passage

The earthquake struck at 3:42 AM on Tuesday. Within hours, rescue teams were deployed. By the end of the week, over 500 survivors had been found. The recovery effort is expected to continue for several months. Officials said that in the past decade, this was the strongest earthquake to hit the region since the devastating 1995 event.

Question 6

List all temporal expressions in the passage and classify them:

What makes "the past decade" difficult to normalize?

Part 7: Group Discussion

Question 7

Compare your annotations with your group. Where did you disagree?

Part 8: Reflection

Question 8

Why is temporal annotation difficult?

Key Takeaway

Time in language is often relative, vague, and context-dependent.

  • Normalization requires a reference point (document creation time)
  • Vague expressions require annotation decisions about precision
  • Temporal relations often require world knowledge and inference
  • The same expression can have different meanings in different contexts