Knowledge Base Retrieval and Recall for Railway and Highway

What the Data for This Category Looks Like

This category’s data comes primarily from publicly released project completion documents, operation and maintenance logs, annual statistical reports, and compliance review documents published by transportation authorities. This data follows two update schedules. New projects receive a full one-time update after completion. Operational lines update operational data such as passenger and freight volume and revenue quarterly. They update line maintenance and expansion and reconstruction information annually. Most documents include standardized engineering parameter fields, such as design speed, traffic capacity, and total budgeted investment. Common units include kilometers, vehicles per day, ten thousand yuan, and other professional engineering units. Long sections of compliance clauses and operational analysis content are interspersed throughout the documents.

What Constraints These Characteristics Impose on the Knowledge Base Retrieval and Recall Link

This category’s data characteristics impose three core constraints on the retrieval and recall process. First, the data contains many standardized professional fields and long text segments. Precise matching of field content is required, and context breaks must be avoided. A reasonable chunking strategy must be adopted. Second, data updates have staged and periodic differences. Index refreshes must balance the immediacy of new project updates and the periodic updates of operational data. A fixed full refresh strategy cannot be used. Third, engineering parameters have extremely high precision requirements. Irrelevant documents with low similarity must be filtered out to avoid recalling general transportation content outside the target category. Additionally, some individual documents have large file sizes. Parsing and index construction must accommodate longer processing times.

How to Configure the Settings

Configuration Item	Recommended Value Range	Rationale
`chunkSize`	800–1200 characters	Railway and highway due diligence reports mostly contain long sections of engineering parameters and compliance clauses. This chunk length balances context integrity and retrieval accuracy
`topK`	Top 8–12 results	This category has many highly specialized data fields. A sufficient number of candidate results must be recalled to avoid missing key engineering parameters
`scoreThreshold`	0.75–0.85	Engineering parameters require high matching accuracy to avoid recalling irrelevant general transportation documents
`refreshInterval`	2:00 AM daily	Operational data is updated quarterly. Daily refreshes ensure index timeliness while avoiding peak business hours
`rerankTopN`	Top 3–5 results	Focus must be placed on core engineering and operational indicators to reduce redundant results and improve retrieval efficiency
`PARSE_FILE_TIMEOUT_SECONDS`	600 seconds	Parsing large completion documents takes a long time. Extending the timeout prevents parsing interruptions

The parameter values provided on this page are common starting points for configuration. Actual values are affected by material format, data volume, and business rules. Specific issues require targeted analysis. It is recommended to test on your own samples before finalizing settings.

Three Common Misconfigurations

Phenomenon: Calls to the knowledge base retrieval interface return results that include general transportation documents unrelated to railways or highways. Some engineering parameter fields are empty or use incorrect units. Cause: No reasonable threshold is set for the scoreThreshold parameter, leading to recall of irrelevant low-similarity documents. Field verification configuration is not enabled.
Phenomenon: A 408 Request Timeout error triggers when parsing a single railway completion report larger than 500MB. Cause: The PARSE_FILE_TIMEOUT_SECONDS configuration is not set to a value above 600 seconds. The default timeout limit is insufficient for long document parsing.
Phenomenon: QA split index creation via OpenAPI takes longer than expected. Cause: The chunkSize is not adjusted to the 800–1200 character range. Too short chunk sizes increase the number of index shards and prolong construction time.

How to Verify Correct Configuration

Upload a typical railway line completion document. Check the parsed chunked content to confirm the chunk length matches the configured chunkSize value.
Submit a retrieval request targeting core railway line parameters. Check if the score field values of returned results exceed the configured scoreThreshold.
Review index refresh logs to confirm automatic index refreshes trigger at 2:00 AM daily, matching the refreshInterval configuration.
Call the knowledge base creation interface via OpenAPI, upload a QA split file, and confirm the task completes without triggering a 408 Request Timeout error.

Question material comes from public community discussions. Configuration values are common starting points and should be measured against your own samples. Verified on 2026-09-14.