# Query Management - Common CQL Artifacts for FHIR (US-Based) v2.0.0-ballot

## Query Management

This topic provides query management guidance for implementers to support the use of CQL within FHIR artifacts such as questionnaires, typically from a DTR application. The functions and guidance provided here facilitate:

* Manage optional server-side parameters
* Check for modifier elements and extensions
* Manage optional _include and _revInclude situations
* Manage _element filtering
* Manage version differences among servers
* Provide simpler functions with typical search parameter filters (e.g. including only final and amended observations)
* Manage extension retrieval for extensions expected to be present (e.g. USCore and CRD extensions)
* Complex element retrieval such as "Cumulative Medication Duration" and "Body Surface Area"
* [Authoring](authoring.md)
* [Patterns](patterns.md)
* Libraries 
* [USCoreCommon](Library-USCoreCommon.md)
* [USCoreElements](Library-USCoreElements.md)
* [USCoreTests](Library-USCoreTests.md)
 

