Self-Ask: Improving Factuality through Iterative Questioning

While architectures like ReAct focus on interleaving reasoning and acting to accomplish tasks, other frameworks prioritize improving the factual grounding and explicit reasoning process behind an LLM's response, especially for complex questions requiring information synthesis. The Self-Ask mechanism addresses this by enabling an agent to explicitly decompose a complex query into a series of simpler, interconnected sub-questions. This iterative process aims to gather necessary factual pieces before attempting a final answer, enhancing traceability and often improving accuracy.

Instead of directly answering a potentially multi-faceted question, the LLM, guided by specific prompting, first determines if the question can be answered directly or if it requires decomposition. If decomposition is needed, the LLM formulates a follow-up question targeting a specific piece of missing information. This sub-question is typically designed to be answerable via an external lookup, often using a search engine or a dedicated knowledge base API. Once the answer to the sub-question is retrieved (let's call this intermediate answer $i_k$), it's fed back into the context. The LLM then assesses if it has enough information to answer the original question or if another follow-up question ($q_{k+1}$) is required. This loop continues until all necessary intermediate facts are gathered, allowing the LLM to synthesize the final, grounded answer.

The Self-Ask Iteration Loop

Consider a question like: "What is the difference in population between the capitals of Malaysia and Thailand?"

A Self-Ask agent would proceed as follows:

1. Initial Analysis: The LLM recognizes the need for specific facts: the capital of Malaysia, the capital of Thailand, and their respective populations.
2. Generate Sub-Question 1: The LLM outputs a follow-up question: Follow-up: What is the capital of Malaysia?
3. External Lookup 1: An external tool (e.g., search API) is invoked with "What is the capital of Malaysia?". It returns Intermediate Answer: Kuala Lumpur.
4. Incorporate Answer & Generate Sub-Question 2: The context now includes "Kuala Lumpur is the capital of Malaysia". The LLM identifies the next missing piece and asks: Follow-up: What is the capital of Thailand?
5. External Lookup 2: The tool searches for "What is the capital of Thailand?" and returns Intermediate Answer: Bangkok.
6. Incorporate Answer & Generate Sub-Question 3: Context updated. Next missing piece: Follow-up: What is the population of Kuala Lumpur?
7. External Lookup 3: Tool searches for "population of Kuala Lumpur", returns Intermediate Answer: ~1.9 million.
8. Incorporate Answer & Generate Sub-Question 4: Context updated. Next: Follow-up: What is the population of Bangkok?
9. External Lookup 4: Tool searches for "population of Bangkok", returns Intermediate Answer: ~10 million.
10. Synthesize Final Answer: All necessary facts are gathered. The LLM now has the capitals (Kuala Lumpur, Bangkok) and populations (~1.9M, ~10M). It calculates the difference and formulates the final response: Final Answer: The difference in population between Kuala Lumpur (~1.9 million) and Bangkok (~10 million) is approximately 8.1 million.

This structured decomposition makes the reasoning process transparent and relies on external tools for factual retrieval, reducing the likelihood of hallucination for the component facts.

The iterative flow of the Self-Ask mechanism. The LLM determines if decomposition is needed, generates sub-questions, utilizes external tools for answers, incorporates results, and repeats until the original question can be answered.

Implementation Details for Expert Systems

Implementing Self-Ask effectively requires careful consideration of several aspects:

• Prompt Engineering: The core of Self-Ask lies in the prompt structure. It must guide the LLM to:

  • Recognize when a question is complex and requires factual decomposition.
  • Explicitly output follow-up questions prefixed with a specific token (e.g., Follow-up:).
  • Signal when an external lookup's result is expected (often by stopping generation after the follow-up question).
  • Use a distinct prefix for the final answer (e.g., Final Answer:).
  • Integrate the intermediate answers (provided by the system after lookup) into its subsequent reasoning steps. This often involves few-shot examples within the prompt demonstrating the desired iterative behavior.

• Tool Integration and Error Handling: The system needs strong integration with the external lookup tool (e.g., a search API wrapper). Failures in this tool (network errors, no results, ambiguous results) must be handled carefully. The agent might need logic to:

  • Rephrase the sub-question and retry.
  • Attempt lookup with an alternative tool or source.
  • Report the inability to find a specific piece of information back to the LLM, allowing it to potentially adjust its strategy or state the limitation in the final answer.

• Managing Iteration Depth: Unconstrained decomposition can lead to excessive latency or cycles. Implementing safeguards is necessary:

  • Maximum Depth: Limit the number of follow-up questions allowed ($k_{max}$).
  • Confidence Scoring: If the LLM can output confidence scores for its need to ask follow-up questions, a threshold can be used.
  • Dependency Analysis: More sophisticated implementations might track the dependency graph of questions to detect cycles or redundant queries.

• Relation to Other Architectures: Self-Ask's strength lies in its structured approach to fact-finding for compositional questions. Unlike ReAct, its primary loop isn't focused on acting within an environment but on refining understanding through targeted information gathering. Compared to Tree of Thoughts (ToT), Self-Ask follows a more linear decomposition path driven by perceived information gaps, whereas ToT explores multiple reasoning branches concurrently. It excels when the path to the answer involves sequentially resolving factual dependencies.

Advantages and Limitations

Advantages:

• Improved Factuality: By grounding intermediate steps in external knowledge sources, Self-Ask can significantly reduce factual errors in the final synthesis.
• Interpretability: The explicit sequence of sub-questions and intermediate answers provides a clear trace of the agent's reasoning process.
• Compositionality: It naturally handles questions that require combining multiple pieces of information.

Limitations:

• Latency: Each iteration involving an external lookup adds latency, making it slower than direct generation.
• Error Propagation: Errors in intermediate answers (from the external tool) or flawed sub-questions (from the LLM) can derail the entire process.
• Tool Dependency: Performance is heavily reliant on the quality and reliability of the external lookup tool.
• Scope: Less suited for tasks demanding creative generation, complex planning involving actions in an environment, or subjective judgments, where factual decomposition isn't the primary challenge.

In summary, Self-Ask represents an important technique for building more reliable and transparent question-answering agents. By forcing a decomposition of complex queries and leveraging external knowledge sources for factual grounding, it provides a structured mechanism to improve the accuracy and trustworthiness of LLM responses in information-intensive scenarios. It's a valuable component in the toolkit for designing advanced agentic systems where factual precision is a high priority.