# Semantic Queries Expression Constraint Language (ECL) is a formal syntax for representing SNOMED CT expression constraints. Expression constraints are computable rules used to define bounded sets of clinical meanings represented by either precoordinated or postcoordinated expressions. Snow Owl includes an editor and execution environment for ECL. All of the operators and grammar constructs defined in the [Expression Constraint Language specification](https://confluence.ihtsdotools.org/display/DOCECL/Expression+Constraint+Language+-+Specification+and+Guide) are supported. Using ECL, you can query concepts by their relationships as opposed to their human-readable descriptions. {% hint style="info" %} You can check out our examples in the Project Explorer view: `Snow Owl_examples/ECL`. {% endhint %} --- # 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.b2ihealthcare.com/snow-owl-authoring-platform/browsing-and-searching/semantic-queries.md?ask= ``` 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.