# dag

## DAG

**This is an abbreviation for directed acyclic graph.**

## directed acyclic graph

A set of nodes connected to one another by lines (edges) in which each connection has a specified direction such that no route that follows the direction of the connections enters a loop (cycle).

#### Notes

* The SNOMED CT subtype hierarchy is a *Directed Acyclic Graph*. SNOMED CT concepts are nodes and subtype relationships are the directed lines that connect them. All subtype relationships lead from a more specific concept to a more general concept, so a cycle would be a logical error (e.g. if "rubella virus" is a type of "virus" and "virus" is a type of "microorganism", then "microorganism" cannot be a type of "rubella virus").

<figure><img src="https://1017548453-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FP21QucCX9Y41nBQt50ad%2Fuploads%2Fgit-blob-c45fd9213c87bdd5ceac785858ccb83caff84963%2F82880191.png?alt=media" alt=""><figcaption><p>Figure 1: Illustrative Example - Directed Acyclic Graph</p></figcaption></figure>

## Alternatives

* **DAG**

## Related Links

* Wikipedia
  * [Directed Acyclic Graph](http://en.wikipedia.org/wiki/Directed_acyclic_graph)

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


---

# Agent Instructions: 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:

```
GET https://docs.snomed.org/snomed-international-documents/snomed-ct-glossary/d/dag.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.