Text Summarization
Text summarization is the process of producing a condensed version of a longer text that retains its key information, main arguments, and essential meaning.
Definition¶
Text summarization is the task of automatically or manually producing a shorter version of a document that preserves the most important content. Summaries reduce length while maintaining the essential meaning, key points, and — for narrative content — the logical structure of the original.
Types of Text Summarization¶
Extractive summarization selects and combines the most important sentences directly from the source text. The output consists of original sentences — nothing is rewritten. Extractive systems are simpler to implement but can produce choppy, context-lacking summaries.
Abstractive summarization generates new sentences that express the source's meaning in fewer words. Modern LLM-based summarizers use this approach, producing fluent summaries that may phrase information differently than the original. This is closer to how humans summarize.
Summarization vs. Paraphrasing¶
| Summarization | Paraphrasing | |
|---|---|---|
| Length | Shorter than source | Similar to source |
| Goal | Condense key information | Re-express in different words |
| Detail | Selective | Complete |
Quality Criteria for Summaries¶
A good summary: - Covers the main argument and key supporting points - Omits minor details, repetition, and examples that aren't essential to the main point - Preserves the logical structure and relationships between ideas - Avoids introducing new information not present in the source - Reads as a standalone document (doesn't require the reader to have read the original)
AI Summarization Quality¶
LLM-based summarizers produce high-quality summaries for structured, factual content. Common failure modes include: - Hallucination — introducing facts not present in the source - Flattening nuance — removing important qualifications that change the meaning - Missing the main argument — summarising supporting points while omitting the thesis
For important documents, human review of AI-generated summaries is recommended.