# Structured data types

This section describes the structured data types which make up OS Open Names. The attributes associated with these data types are listed below along with a brief description of their data properties.

### **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.

### **Size**

The length of the attribute provided (optional).

### **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.