# Annotations

The purpose of annotations is to provide a formal means to represent additional information about a SNOMED CT component (concept, description, relationship) or as a member of a reference set.

Annotations are:

* a form of metadata
* optional and non-defining
* constructed by following the Object-Attribute-Value pattern and stored either in annotation refsets or relationship files.

Each annotation uses a subtype of 1295447006 | Annotation attribute (attribute)| to represent the type of annotation with an annotation attribute value.

## Use case

Attribution - Attributing credit to the source of information

For example,

* *Inserm Orphanet* attribution annotation at 1332326002 |Isolated cleft lip (disorder)|

<figure><img src="https://4060284305-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FuoSxuN6wQMDYcvuq2wNX%2Fuploads%2Fgit-blob-e210c027d0a8eb1063d7f65cb8a6eb08f59257b4%2F273519000.png?alt=media" alt=""><figcaption><p>Figure shows attribution annotation is located in details tab of 1332326002 |Isolated cleft lip (disorder)| in the browser</p></figcaption></figure>

{% hint style="success" %}
SNOMED derivative products, such as mappings to/from other terminologies, should not be represented as annotations. Refsets have been developed for different types of maps which includes additional metadata, such as map group, priority, rule, and advice.
{% endhint %}

## Guidance

Annotations can be:

* added to both new and legacy concepts.
  * For legacy concepts, attribution may only be added if there is a change to the modeling of the concept to support the collaborating organization's definition.&#x20;
* added in the international edition or extensions.
* inactivated if incorrect or no longer relevant. An inactivation reason is not required. Each annotation attribute has its own requirements and rules on maintenance documented in separate guidance.

Annotations in annotation refsets can be found by using ECL queries for refset members. Currently, there is only data in the refset called *Component annotation refset with string value* , so the following ECL query yields all SNOMED CT concepts currently with an annotation:

{% code overflow="wrap" %}

```
^ 1292992004 |Component annotation with string value reference set (foundation metadata concept)|
```

{% endcode %}

{% hint style="warning" %}
Concepts with annotations cannot be found by using text search in the browser.
{% endhint %}

Annotation length is restricted up to 4000 characters and are represented by the *String* data type which allows URL, number, and text for annotation values. Each annotation attribute should state the allowed values.

For example,

* If an attribute is only allowed for taking numbers, then URL or text should not be used for its values, because numbers are saved in different formats; numbers are saved with a prefix # and text is quoted.

The following are documented in the respective annotation guidance, if applicable.

* Maintenance process
* Validation for annotations, such as spell check
* Annotation cardinality - Most attributes will be 0..1 but some may allow multiple values.

See also [SNOMED CT Annotations](https://conf.spaces.snomed.org/wiki/spaces/mag/pages/133137753/SNOMED+CT+Annotations) for more information.

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