> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/~/changes/AJZwzCsyrD9hiTbOxIbO/identifiers/os-open-linked-identifiers/os-open-linked-identifiers-technical-specification/blpu_uprn_roadlink_toid_9.md).
# BLPU\_UPRN\_RoadLink\_TOID\_9
This page aims to provide all the information to evaluate if the method of associating the respective identifiers is suitable for your needs. These identifier relationships have been extracted from existing premium products and are presented in a standalone table for easy and open access to the information. It describes which product the information was extracted from, what information was extracted and how the source product derived the original association between the identifiers.
Identifiers displayed on OS Map data showing RoadLink and Topographic area feature types
## Relationship Extraction
The relationship between the Unique Property Reference Number (UPRN) and the Topographic Identifier (TOID) of *OS MasterMap Highways Network - Roads* is extracted for all live, provisional and historic BLPU records in *AddressBase Premium*. Data from the *OS MasterMap Highways Network - Roads* and *AddressBase Premium BLPU* table are joined where the TOID equals the CROSS\_REFERENCE of the AddressBase Premium Cross-Reference table and the source is equal to ‘7666MI’.
The relationship is extracted from *AddressBase Premium* after the release of each six weekly Epoch. Further information on the relationship extraction, including the date of extraction and product version information, are provided in the Product Version Information File.
## Correlation Method
The relationship is determined by finding the closest RoadLink TOID from *OS MasterMap Highways Network – Roads*, to every BLPU of *AddressBase Premium* that references a USRN. The relationship is performed by [GeoPlace,](https://www.geoplace.co.uk/) a joint venture between Ordnance Survey and Local Government Association (LGA) who produce *AddressBase*.
*AddressBase Premium* is updated every six weeks and *OS MasterMap Highways – Roads* is updated every four weeks. Therefore, some of the version information in the product may have changed and mean that the relationship is out of sync. To provide an indication of the reliability of the version information provided in this product in relation to that of the version of the features used to form the correlation in the original product, a Confidence Value is given for each relationship, which is defined as follows:
| Confidence Value | Definition |
| ------------------------------------------- | ------------------------------------------------------------------------------------------------------------------- |
| Version information is correct | The version information provided is the same as the version of the feature used to create the correlation. |
| Version information has potentially changed | The version information could be different from the version of the feature that was used to create the correlation. |
| Version information has changed | The version information provided is different from the version of the feature used to create the correlation. |
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://docs.os.uk/os-downloads/~/changes/AJZwzCsyrD9hiTbOxIbO/identifiers/os-open-linked-identifiers/os-open-linked-identifiers-technical-specification/blpu_uprn_roadlink_toid_9.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
