> 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/products/buildings-and-infrastructure-portfolio/os-open-linked-identifiers/os-open-linked-identifiers-technical-specification/linked-identifier-data-csv-attributes.md).

# Linked Identifier data (CSV) attributes

This section provides the following information about each attribute of the CSV product:

### Name and Description

The name of the attribute and what it is describing.

### Type

The nature of the attribute, for example a numeric value or a code list value.

### Multiplicity

Describes how many times this element is expected to be populated in the data. An attribute may be optional or mandatory; these are denoted by:

* ‘1’ – Mandatory - There must be a value.
* ‘0..1’ – Optional – If populated a maximum of one attribute will be returned. These values may be used in combination.

## Linked Identifier data attributes <a href="#bookmark3" id="bookmark3"></a>

### RELATIONSHIP\_ID

Unique identifier for the relationship. Made up of a concatenated string in the format: {Data Identifier 1}*{Feature Identifier 1}*{Data Identifier 2}*{Feature Identifier 2}*{CorrelationType Number}

* **Type**: text
* **Multiplicity**: \[1]

### IDENTIFIER\_1

The primary identifier of Source Dataset 1.

* **Type**: text
* **Multiplicity**: \[1]

### VERSION\_NUMBER\_1

Version number of the primary identifier of Source Dataset 1. Where available, NULL otherwise.

* **Type**: integer
* **Multiplicity**: \[0..1]

### VERSION\_DATE\_1

Version date of the primary identifier of Source Dataset 1. Where available, NULL otherwise.

* **Type**: date time
* **Multiplicity**: \[0..1]

### IDENTIFIER\_2

The primary identifier of Source Dataset 2.

* **Type**: text
* **Multiplicity**: \[1]

### VERSION\_NUMBER\_2

Version number of the primary identifier of Source Dataset 2. Where available, NULL otherwise.

* **Type**: integer
* **Multiplicity**: \[0..1]

### VERSION\_DATE\_2

Version date of the primary identifier of Source Dataset 2. Where available, NULL otherwise.

* **Type**: date time
* **Multiplicity**: \[0..1]

### CONFIDENCE

Confidence value based on a comparison of feature dates between the two source features. Can be one of:

* Version information is correct
* Version information has potentially changed
* Version information has changed
* **Type**: text
* **Multiplicity**: \[1]
* **Notes**: May be a constant value of the possible ones for certain relationships.


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