> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-international-documents/snomed-ct-glossary/c/canonical-form.md).

# canonical form

## canonical form

A serialized representation of a SNOMED CT expression produced by applying a set of rules that ensure a single unique representation for any expression.

#### Notes

* Expressions that contain exactly the same concept identifiers and refinements, may differ from one another in the following ways:
  * Inclusion of whitespace between elements
  * Inclusion of specific terms associated with identified concepts.
  * The order in which focus concepts, refinements, attributes, and attribute groups appear.
* The *canonical form* is generated by removing whitespace and terms from an expression and arranging the focus concepts, refinements, attributes, and attribute groups in a standard order.
* If *canonical form* rules are applied to a normal form expression, the result is a single unique rendering of the meaning represented by that expression.

## Alternatives

* **Canonical representation**

## Related Links

* Wikipedia
  * [Canonical form](https://en.wikipedia.org/wiki/Canonical_form)

<a href="https://docs.google.com/forms/d/e/1FAIpQLScTmbZIf0UEQwYDkY27EEWBkaiYkHSbR0_9DmFrMLXoQLyL7Q/viewform?usp=pp_url&#x26;entry.1767247133=SNOMED+Glossary&#x26;entry.670899847=canonical%20form" class="button primary">Provide Feedback</a>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.snomed.org/snomed-international-documents/snomed-ct-glossary/c/canonical-form.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.