> 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/snowray-v1.1.1/reference/resources/codesystems.md).

# Code Systems

Code systems contain all the relevant concepts that can be utilized to create [value sets](/snowray/snowray-v1.1.1/reference/resources/valuesets.md) and [concept maps](/snowray/snowray-v1.1.1/reference/resources/conceptmaps.md). Snowray mainly supports [SNOMED CT](https://www.snomed.org) and local code systems.

{% hint style="info" %}
🧐 Can't find a resource? Please visit the [Find a Resource](/snowray/snowray-v1.1.1/reference/resources.md#find-a-resource) section.
{% endhint %}

## 🔎 Browsing

The selected code systems can be browsed by pressing the![](https://1046423764-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MfXbzY7oaJUjXyvlBQk%2Fuploads%2Fgit-blob-753b22d2e8a078825f1fef045b900acadb7c2ad4%2Fbrowse_button.png?alt=media)button in the upper right corner, after which the content of the code system is displayed in a tree hierarchy.

![Browse Code System Versions](https://1046423764-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MfXbzY7oaJUjXyvlBQk%2Fuploads%2Fgit-blob-52337ef12d0bc08933d5011e3fd5bdcd1650459b%2Fcode_system_change_version.gif?alt=media)

Users can browse the different versions of code systems while browsing by clicking on the code system's title.

### Searching Concepts

Clicking the small triangles next to the parent concepts enables users to search for [concepts](#concepts) by expanding the tree. Besides this aforementioned manual approach, another option offers to use the filter search for lexical matches.

In addition, Snowray also provides an[ advanced search](/snowray/snowray-v1.1.1/reference/resources/codesystems/search.md) option, which can be invoked by pressing the![](https://1046423764-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MfXbzY7oaJUjXyvlBQk%2Fuploads%2Fgit-blob-8335b5155f2a73437afe0938cfaa01f12b0a3029%2Fadvanced_search_icon.png?alt=media)advanced filter icon in the search bar. This enables users to specify additional criteria to restrict their searches.

![Advanced Filter](https://1046423764-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MfXbzY7oaJUjXyvlBQk%2Fuploads%2Fgit-blob-4ee7808c4f516e5851d674f8f5a80a122766feb9%2Fadvanced_filter_search.png?alt=media)

Most of the filters are dropdowns except for the [ECL](https://confluence.ihtsdotools.org/display/DOCECL) filter, which requires typing in a valid query. A content assist, which can be activated by pressing `Ctrl` + `Space` , helps users to construct [ECL](https://confluence.ihtsdotools.org/display/DOCECL) queries easily.

## 📍 Concepts

When browsing a code system, selecting a [concept](#concepts) navigates users to the concept details. On the ***Overview tab*** the descriptions, properties, and metadata are revealed. Some of the content is displayed with blue color, which indicates that it is a link to another concept. Clicking on those links navigates users to the linked concept's detail page.

![Linking between Concepts](https://1046423764-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MfXbzY7oaJUjXyvlBQk%2Fuploads%2Fgit-blob-405b82e1d135b5251818b11a8ad750fa510ca4a1%2Flinking.gif?alt=media)

{% hint style="info" %}
Concepts are read-only resources and can be browsed only within a code system.
{% endhint %}

The ***History tab*** displays the changes made to the [concept](#concepts). Each change is represented on a timeline and has an individual node. The nodes display the modifier's e-mail address and the elapsed time since the change in their title, while the action that modified the concept can be found in the details part.

![Concept History](https://1046423764-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MfXbzY7oaJUjXyvlBQk%2Fuploads%2Fgit-blob-07bc58c1da12162ce2030e7d9b3f388b2f8ae595%2Fconcept_history.png?alt=media)