> 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/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-technical-specification/structured-data-types.md).

# Structured data types

This section describes the structured data types which make up OS MasterMap Water Network Layer:

* [LinearReference](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-technical-specification/structured-data-types/linearreference.md)
* [PointReference](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-technical-specification/structured-data-types/pointreference.md)

The attributes associated with each data type are listed on the individual structured data type pages.

## Structured data type attribute information

The following information will be provided against each attribute.

### **Name and Definition**

The name of the attribute and what it is describing.

### **Data 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 within the product. These are denoted by:

* ‘1’ – there must be a value.
* ‘0..1’ – population is optional but a maximum of one attribute will be returned. These values may be used in combination.


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