Retrieval-Augmented Summarisation
Overview
Retrieval-Augmented Summarisation combines two processes:- Retrieval: Find the most relevant documents or document chunks.
- Summarisation: Generate a concise summary using the retrieved information.
1. Why Retrieval-Augmented Summarisation?
Traditional summarisation usually works like this:- There are many documents.
- Documents are too large.
- Only specific information is needed.
- The context exceeds the model’s context window.
- Irrelevant information affects the summary.
2. Basic Workflow
The complete process has two main stages.Stage 1: Retrieval
Stage 2: Summarisation
The retrieved documents are passed to the language model.3. Core Components
A Retrieval-Augmented Summarisation system typically contains:
The architecture is:
4. Summarisation With Context From Retrieved Documents
The main idea is to give the model a selected context. Suppose the knowledge base contains 1,000 documents. A query is:- More focused
- More efficient
- More relevant to the query
- Less likely to include unrelated information
5. Building the Context
Retrieved documents are usually combined into a single context string. Example:6. Prompt Design for Summarisation
Prompt design is important because it determines:- What information should be included.
- How long the summary should be.
- What style should be used.
- Whether unsupported information should be avoided.
7. Query-Focused Summarisation
A useful type of Retrieval-Augmented Summarisation is query-focused summarisation. The summary is generated based on a specific query. Example:8. Generic vs Query-Focused Summarisation
Generic Summarisation
The system summarises the retrieved content without a specific focus.Query-Focused Summarisation
The query determines what should be included in the summary.9. Important Prompt Parameters
A summarisation prompt can define several constraints.Summary Length
Output Format
Grounding
Missing Information Handling
10. A Strong Summarisation Prompt
A more complete prompt can be:11. Retrieval Quality Affects Summary Quality
The summarisation model can only summarise the information it receives.12. Important Retrieval Parameters
Top-k
k determines how many documents are retrieved.
Similarity Search
Documents are retrieved based on semantic similarity.Chunk Size
Large documents are usually split before indexing.- Retrieval may be less precise.
- More irrelevant information is included.
- Important context may be split across multiple chunks.