What this type of data looks like
Data for urban public transit policy and regulatory basis questions mainly comes from official public documents issued by the Ministry of Transport and local municipal transportation authorities. The update schedule is triggered when new policies are released or local operational regulations are revised. Most documents follow formal official document structure, including fields such as policy document number, issuing authority, effective date, and clause entries. Content is divided by chapter and clause hierarchy, and individual documents vary significantly in length; some regional operational specification documents can span dozens of pages.
Constraints imposed by these characteristics on citation sources and traceability
The long length and hierarchical structure of urban public transit policy documents require that citation traceability retain precise clause-level matching to avoid incorrect cross-clause associations. The fixed document number and issuing authority fields in official documents require that traceability results display these corresponding identifiers to facilitate verification by operation and maintenance personnel. The random update cycle of regional policies requires that the knowledge base synchronization mechanism support incremental updates by policy document number, avoiding redundant operations from full re-imports. Chunking of long documents must match the original chapter hierarchy to prevent citation fragments from being separated from the original policy context due to improper segmentation.
How to set configurations
| Configuration Item | Recommended Approach | Rationale |
|---|---|---|
| Chunk Overlap Length | 80–120 characters | Urban public transit policy documents are mostly hierarchical clauses. Overlap length preserves contextual association between adjacent clauses and avoids slicing that breaks policy logic |
quoteMaxToken | 1500–2000 token | Single clauses in urban public transit policies have relatively long content. This value range fully retains the complete semantics of citation fragments while controlling context length |
responseData | Enable citation detail mode | Requires returning original document fragments and metadata for citations to meet verification needs for policy traceability |
detail | Return complete metadata fields | Urban public transit policies require displaying metadata such as document number and issuing authority to facilitate verification of policy sources by operation and maintenance personnel and the public |
| Retrieval Matching Threshold | Calibrate based on actual testing | Different cities have distinct wording styles for policy documents. Adjust the threshold based on actual retrieval results to ensure precise matching |
Three common configuration errors
- Symptom: The terminal response does not display citation fragments. Cause: The detail configuration corresponding to
responseDatais not enabled, causing the API to not return citation metadata. - Symptom: Citation fragments do not match the original policy clause content. Cause: The chapter hierarchy structure of the policy was not preserved during chunking, causing slicing to separate the clause context association.
- Symptom: The API call returns an error status code. Cause: The
quoteMaxTokenvalue exceeds the maximum context limit supported by the model, resulting in invalid request parameters.
How to confirm the configuration is properly set
- Call the FastGPT v4.17.0 knowledge base question answering API, and check if the returned results include citation fragments and metadata fields.
- Enter the knowledge base management page, view the chunk details, and confirm that the chunks retain metadata such as policy document number and issuing authority.
- Simulate a query for a specific urban public transit operational policy clause, and verify that the returned citation fragments match the original document content.
- Trigger an incremental update task for the knowledge base, and confirm that subsequent queries can associate with the latest version of policy documents.
The values provided are common starting points and should be measured against the reader's own samples.
Question material comes from public community discussions. Configuration values are common starting points and should be measured against your own samples. Verified on 2026-09-28.