What this category of data looks like
This category of data primarily originates from the unified national land and spatial planning map, project approval and supervision platform, current land use database, and ecological protection redline data. Updates occur on an irregular basis. Documents processed daily include land pre-examination and site selection opinions, construction land planning permits, construction engineering planning permits, supporting instructions for redline diagrams, planning conditions, and similar materials. Core fields cover project site selection, land use scale, redline scope, planning control requirements, and other related items. These data are maintained jointly by the land and natural resource authority’s land use control and planning permit division, administrative examination and approval bureaus, and project units.
What constraints do these characteristics impose on the vector model and index link
The data sources for this category are scattered, and updates follow no fixed cycle. The index system must support incremental updates and multi-source data fusion. Documents processed daily have diverse types, including approval documents, supporting instructions for planning drawings, and control rule texts. The semantic granularity of different documents varies significantly. Targeted adjustments to chunking logic are required to meet the semantic retrieval needs of policy Q&A. Core fields involve rigid requirements for land use control. Retrieval results must strictly match the expression boundaries of official policy texts, to avoid generalization deviations from semantic retrieval. Additionally, format differences between application materials submitted by project units and official data require standardized processing before indexing, to ensure consistency in vectorization.
How to set the configurations
| Configuration Item | Recommended Value | Rationale |
|---|---|---|
| Chunk Length | 800–1200 characters | Aligns with the semantic integrity of policy text paragraphs, avoids splitting that disrupts the context of control rules |
| Overlap Length | 100–200 characters | Preserves policy connection logic across chunks, prevents key control requirements from being split apart |
| Similarity Threshold | 0.75–0.85, calibrated via actual testing | Meets the strictness requirements of land use policies, filters out low-correlation generalized retrieval results |
| defaultToken | 4096 | Aligns with the single context length requirements of policy documents |
| maxToken | 8192 | Supports integrating associated content from multiple approval documents |
| Single Search Limit | Top 10 results | Controls the number of retrieval results, avoids redundant information interfering with policy verification |
Three common mistakes
- Phenomenon: Semantic retrieval returns extremely high scores, but the content is unrelated to land use policy basis. Cause: No reasonable similarity threshold set for rigid control fields of land use policies, leading to generalized semantic matching interfering with accurate recall.
- Phenomenon: Auxiliary data uploaded but does not appear in retrieval results. Cause: The vectorization index switch for auxiliary data is not enabled, or auxiliary data is not associated with the index task of the corresponding knowledge base.
- Phenomenon: Vector files generated using a custom vector model locally cannot be retrieved normally after being uploaded to the server. Cause: The generation parameters of the vector model are not unified, resulting in a mismatch between the server-side vector index and local vectors.
How to confirm configurations are properly set
- Manually upload a typical land pre-examination policy document, check if the chunked content retains complete control clauses, with no key content truncated.
- Initiate a test query targeting planning control requirements, verify that the similarity scores of retrieval results meet the preset strictness requirements.
- Submit an updated official data set, verify that the index system completes incremental updates, and the new data can be retrieved normally.
- View the knowledge base index logs, confirm that all configuration item parameters have been loaded correctly, with no error records.
The values provided here are common starting points, and should be evaluated 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.