> For the complete documentation index, see [llms.txt](https://docs.b2ihealthcare.com/snowray/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.b2ihealthcare.com/snowray/v3.1/reference/resources/codesystems/custom-code-systems.md).

# Custom Code Systems

Besides the existing Terminology Standards, Snowray supports the creation and maintenance of Custom Code Systems that consist of a set of terms.  

## Schema

The Schema provides a structure to Custom Code Systems through different property types. The Code System Schema has a dedicated page where the property types can be specified. Defining properties in the Schema is not mandatory, but it definitely helps to construct a more layered Code System structure. In addition to specifying property types, users can also set a cardinality to the given property in order to establish the potential number of values. 

{% tabs %}
{% tab title="Property Types" %}

| Property Type | Description                                                                              |
| ------------- | ---------------------------------------------------------------------------------------- |
| **Boolean**   | *True* or *false* type properties                                                        |
| **Integer**   | Properties with integer number values                                                    |
| **Decimal**   | Properties with decimal number values                                                    |
| **String**    | Text type properties                                                                     |
| **Date**      | Date type properties                                                                     |
| **URI**       | [Uniform Resource Identifier](https://en.wikipedia.org/wiki/Uniform_Resource_Identifier) |
| {% endtab %}  |                                                                                          |

{% tab title="Cardinality" %}

<table><thead><tr><th width="191.9349593495935">Cardinality</th><th>Description</th></tr></thead><tbody><tr><td><strong>0..0</strong></td><td>Not allowed</td></tr><tr><td><strong>0..1</strong></td><td>Optional</td></tr><tr><td><strong>0..*</strong></td><td>Any</td></tr><tr><td><strong>1..1</strong></td><td>Mandatory</td></tr><tr><td><strong>1..*</strong></td><td>Minimum one mandatory</td></tr></tbody></table>
{% endtab %}
{% endtabs %}

## Concept

Concepts are the foundation of all Code Systems. In case of Custom Code Systems, these are usually a list of terms with their associated IDs.

{% hint style="info" %}
If no ID is available for the terms, the system will automatically allocate one during concept creation.
{% endhint %}