# Item Types¶

Item types are the identified entities in your model. They consist of definitions and properties. Properties can be simple types, composite types, or relationships to other item types.

Each item type is defined in a folder located at baseDirectory/ItemTypes/ItemTypeName. Within this folder, several files provide information about the item type.

The baseDirectory/ItemTypes/ItemTypeName/readme.markdown file contains text to describe your item type.

See https://daringfireball.net/projects/markdown/basics for a primer on using markdown to format text.

## ItemTypeName.csv¶

The baseDirectory/ItemTypes/ItemTypeName/ItemTypeName.csv file describes the properties of the item type. Be sure to replace ItemTypeName with the name of the item type.

The CSV file contains the following columns.

Name

The name of the property.

Note

An item type can include a property with the same name as a property in another item type. However, the data types of the properties must be the same.

DataType

The data type of the property. The data type can be one of:

MinCardinality
The minimum number of occurrences of the property that an instance can include. Use 0 to mark the property as optional. Use 1 to mark the property as required.
MaxCardinality
The maximum number of occurrences of the property that an instance can include. Use 1 if the property can only appear a single time. Use n to allow an unlimited number of occurrences.
Description
The description of the property. This is included in the generated documentation, and as comments or annotations in many of the other publishers.
MinLength, MaxLength, Enumeration, Pattern, MinInclusive, MinExclusive, MaxInclusive, MaxExclusive
Used to restrict the allowed values of properties of simple, primitive types as described in Primitive Types.
DeprecatedNamespace, DeprecatedElementOrAttribute, DeprecatedChoiceGroup
Deprecated. Used only for DDI 3.x backward compatibility.

## Extends.*¶

The baseDirectory/ItemTypes/ItemTypeName/Extends.BaseItemTypeName file acts as a marker to indicate that the item type derives from another item type. Derived item types inherit all properties from their parent item type. Be sure to replace BaseItemTypeName with the name of another item type.

This file is optional; it is only needed if the item type derives from another item type.

## Identification¶

All item types are identified using properties as specified in Identification. The properties listed in the baseDirectory/Settings/Identification.csv file are included as properties in all item types.