> 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-ct-specifications/snomed-ct-expression-constraint-language/appendices/appendix-a-examples-of-valid-expressions/a6-nested-expression-constraints-valid-expressions.md).

# Nested Expression Constraints - Valid Expressions

<table data-full-width="true"><thead><tr><th width="361.171875">Expression Constraint</th><th width="254.9375">Precoordinated</th><th>Postcoordinated</th></tr></thead><tbody><tr><td>&#x3C;&#x3C; (^ 700043003 | Example problem list concepts reference set| )</td><td>394659003 | Acute coronary syndrome|</td><td>194828000 | Angina| : 255234002 | After| = 22298006 | Myocardial infarction| 194828000 | Angina| 371807002 | Atypical angina|</td></tr><tr><td>^ (&#x3C; 450973005 | GP/FP health issue reference set| )</td><td>140004 | Chronic pharyngitis|</td><td>297009 | Acute myringitis|</td></tr><tr><td>(&#x3C; 404684003 | Clinical finding| : 363698007 | Finding site| = &#x3C;&#x3C; 39057004 | Pulmonary valve structure| ) AND ^ 700043003 | Example problem list concepts reference set|</td><td>204351007 | Fallot’s trilogy|</td><td>457652006 | Calcification of pulmonary valve|</td></tr><tr><td>(&#x3C; 404684003 | Clinical finding| : 363698007 | Finding site| = &#x3C;&#x3C; 39057004 | Pulmonary valve structure| ) AND (&#x3C; 64572001 | Disease| : 116676008 | Associated morphology| = &#x3C;&#x3C; 415582006 | Stenosis| )</td><td>204351007 | Fallot’s trilogy|</td><td>19036004 | Rheumatic heart valve stenosis| : { 363698007 | Finding site| = 39057004 | Pulmonary valve structure| , 116676008 | Associated morphology| = 415582006 | Stenosis| } 56786000 | Pulmonic valve stenosis|</td></tr><tr><td>(&#x3C;&#x3C; 17636008 | Specimen collection| : 424226004 | Using device| = &#x3C;&#x3C; 19923001 | Catheter| ) . 363701004 | Direct substance|</td><td>78014005 | Urine|</td><td>87612001 | Blood|</td></tr><tr><td>(&#x3C;&#x3C; 404684003 | Clinical finding (finding)| OR &#x3C;&#x3C; 272379006 | Event (event)| ) : 255234002 | After| = &#x3C;&#x3C; 71388002 | Procedure (procedure)|</td><td>235948002 | Postoperative acute pancreatitis|</td><td>64572001 | Disease| : { 370135005 | Pathological process| = 441862004 | Infectious process| , 255234002 | After| = 387713003 | Surgical procedure| , 116676008 | Associated morphology| = 112633009 | Surgical wound| } 441795000 | Infected seroma after surgical procedure|</td></tr><tr><td>&#x3C;&#x3C; 125605004 | Fracture of bone| : [0..0] ((&#x3C;&#x3C; 410662002 | Concept model attribute| MINUS 363698007 | Finding site| ) MINUS 116676008 | Associated morphology| ) = *</td><td>125605004 | Fracture of bone|</td><td>64572001 | Disease| : { 363698007 | Finding site| = 71341001 | Bone structure of femur| , 116676008 | Associated morphology| = 20946005 | Fracture, closed| } 439987009 | Open fracture of bone|</td></tr><tr><td>&#x3C; 404684003 | Clinical finding| : 47429007 | Associated with| = (&#x3C; 404684003 | Clinical finding| : 116676008 | Associated morphology| = &#x3C;&#x3C; 55641003 | Infarct| )</td><td>71023004 | Pericarditis secondary to acute myocardial infarction|</td><td>3238004 | Pericarditis (disorder)| : 47429007 | Associated with| = 57054005 | Acute myocardial infarction|</td></tr></tbody></table>

{% hint style="info" %}
Where necessary, these examples make some assumptions about the membership of the example reference sets.
{% endhint %}

<a href="https://docs.google.com/forms/d/e/1FAIpQLScTmbZIf0UEQwYDkY27EEWBkaiYkHSbR0_9DmFrMLXoQLyL7Q/viewform?usp=pp_url&#x26;entry.1767247133=ECL+Specification&#x26;entry.670899847=Nested%20Expression%20Constraints%20-%20Valid%20Expressions" 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-ct-specifications/snomed-ct-expression-constraint-language/appendices/appendix-a-examples-of-valid-expressions/a6-nested-expression-constraints-valid-expressions.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.