Executing Digital Quality Measures (dQMs) - $cql, $evaluate, $evaluate-measure, $data-requirements

Note

The features described on this page are available in the following Firely Server editions:

Firely dQM - 🌍 / 🇺🇸

Important

Please see Digital Quality Measures for an introduction to Digital Quality Reporting in FHIR.

FHIR provides several mechanisms for executing dQMs, either in full or in part. The appropriate operation depends on the specific use case and execution goal:

Library/$evaluate is most commonly used for debugging purposes. dQMs frequently reference multiple Library resources to encapsulate modular logic. When a measure produces unexpected results—such as an incorrect or zero score—it is often useful to investigate why a particular subject meets or fails to meet specific population criteria (e.g., initial population, denominator, numerator). In such cases, it can be helpful to execute a targeted set of CQL expressions or evaluate specific sub-libraries within the measure. This allows implementers to isolate and verify individual components of the logic without executing the entire measure.
Measure/$measure-evaluate is the primary operation for executing a digital quality measure (dQM) as a whole. This operation evaluates a Measure resource against a specified subject (such as a patient, group) using the measurement period and any associated Library parameters. Measure/$evaluate-measure is typically used in production or formal testing scenarios to generate actual measure scores. It is also suitable for automated execution in quality reporting workflows. Unlike Library/$evaluate, which targets specific expressions, Measure/$evaluate-measure executes the full population logic and scoring methodology defined in the measure, making it the most comprehensive method for end-to-end dQM evaluation.

For the preperation of the execution data-requirements can be gathered using the following operations:

Library/$data-requirements retrieves a structured representation of the data required to evaluate a measure, making it a supporting operation for both Library/$evaluate and Measure/$evaluate-measure. This operation identifies the necessary FHIR data types and elements, including value sets, code filters, and date constraints. It returns a Library resource containing DataRequirement elements, which describe the expected inputs for measure evaluation. This operation is particularly useful during implementation, data mapping, and integration planning, as it helps clarify what data must be available for successful execution of a digital quality measure.
Measure/$data-requirements functions identically, but aggregates the data requirements across all libraries referenced by the measure, providing a complete picture of the inputs needed for measure evaluation.
$cql allows direct execution of CQL expressions, either inline or from referenced libraries. It is useful for rapid testing or prototyping when measure logic needs to be validated independently of a Measure resource.

Library/$evaluate

Firely Server’s implementation of Library/$evaluate is based on version 2.0.0 of the Using CQL with FHIR Implementation Guide. For the formal specification of this operation, refer to the CQL Library Evaluate OperationDefinition.

Supported parameters

Firely Server supports the following parameters:

Parameter	Supported	Type	Additional Notes
`url`	✅	`canonical`	Specifies the `Library` to evaluate via canonical URL. Earlier versions of the IG used `library` for this. Since v2.0.0, `library` is redefined to pass an inline `Library` resource. Firely Server uses `url` only for external logic. Versioned canonical references are allowed, e.g., `http://example.org/fhir/ Library/MyLogic\|1.0.0`.
`library`	✅	`Library` resource	In-line logic library that contains executable CQL logic. This Library will not be stored in Firely Server. It MAY only contain CQL and will be compiled dynamically. If ELM content is provided, it will be re-used.
`subject`	✅	`string`	Only Patient references are supported, may be omitted if no “context Patient” is included in the library.
`expression`	✅	`reference`	The name of the expression to evaluate. If omitted, all expressions in the library are evaluated. CQL Access Modifier extensions are not taken into account.
`parameters`	✅	`Parameters` resource	Input parameters passed into the evaluation context. These will be mapped from FHIR data types to CQL data types according to the FHIR Type Mapping. Most notably, this includes passing in the measurement period parameter as a FHIR Period.
`raw`	✅	`boolean`	Return the library results as a string without mapping the CQL result data types back to FHIR. This is a proprietary parameter of Firely Server.
`useServerData`	✅	`boolean`	When `true`, claims and clinical data are retrieved from the Firely Server database where the operation is executed. When `false`, claims and clinical data are retrieved from the `dataEndpoint` parameter. In both cases, any data passed via the `data` parameter takes precedence.
`data`	✅	`Bundle`	Inline FHIR data bundle to use as the data context during evaluation. The bundle type SHOULD be either `collection` or `searchset` (as the output of a $everything operation).
`dataEndpoint`	✅	`Endpoint` resource	Used only when `useServerData` is `false`. Defines the external FHIR endpoint from which claims and clinical data are retrieved. The endpoint must be pre-registered in `LibraryEvaluateOperation` via the `DataEndpoint` option. See Quality Measure Operations. Data supplied via the `data` parameter always takes precedence.
`prefetchData`	❌	Complex
`includePrivate`	❌	`boolean`
`contentEndpoint`	❌	`Endpoint` resource
`terminologyEndpoint`	❌	`Endpoint` resource	External terminology services should be configured via the Terminology services options.

Important

If the Library references any ValueSet resources, they must be preloaded into the Firely Server’s administration endpoint before executing the Library.

The Library/$evaluate operation is supported as a POST request on both the type and instance levels. Additionally, the instance-level operation may also be invoked using GET.

Example: Type-Level Library/$evaluate Invocation

This example evaluates the bp-check-logic library (version 1.0.0) against a specific patient and a defined measurement period using a POST request to the type-level operation.

Request

POST [base]/Library/$evaluate HTTP/1.1
Content-Type: application/fhir+json

Request Body

{
  "resourceType": "Parameters",
  "parameter": [
    {
      "name": "url",
      "valueCanonical": "http://example.org/fhir/Library/bp-check-logic|1.0.0"
    },
    {
      "name": "subject",
      "valueString": "Patient/cql-patient-test"
    },
    {
      "name": "parameters",
      "resource": {
        "resourceType": "Parameters",
        "parameter": [
          {
            "name": "Measurement Period",
            "valuePeriod": {
              "start": "2023-01-01",
              "end": "2023-12-01"
            }
          }
        ]
      }
    }
  ]
}

Response Body

Given matching input data, specifically, a Patient resource and an Observation with a code of 8480-6 from the LOINC CodeSystem, and an effectiveDateTime that falls within the measurement period — the following output will be returned:

{
  "resourceType": "Parameters",
  "parameter": [
    {
      "extension": [
        {
          "url": "http://hl7.org/fhir/StructureDefinition/cqf-cqlType",
          "valueString": "Fhir"
        }
      ],
      "name": "Patient",
      "resource": {
        "resourceType": "Patient",
        "id": "cql-blood-pressure-check-test-match",
        "meta": {
          "versionId": "d36e61f8-300a-4c2f-8247-9fb4a6837236",
          "lastUpdated": "2025-05-23T18:32:44.106+00:00"
        },
        "birthDate": "1990-06-15"
      }
    },
    {
      "extension": [
        {
          "url": "http://hl7.org/fhir/StructureDefinition/cqf-cqlType",
          "valueString": "Boolean"
        }
      ],
      "name": "HasBPReading",
      "valueBoolean": true
    },
    {
      "extension": [
        {
          "url": "http://hl7.org/fhir/StructureDefinition/cqf-cqlType",
          "valueString": "Boolean"
        }
      ],
      "name": "AdultPatients",
      "valueBoolean": true
    }
  ]
}

$cql

Firely Server’s implementation of $cql is based on version 2.0.0 of the Using CQL with FHIR Implementation Guide. For the formal specification of this operation, refer to the $cql OperationDefinition.

Supported parameters

Firely Server supports the following parameters:

Parameter	Supported	Type	Additional Notes
`expression`	✅	`string`	Specifies an inline CQL expression to be executed. Only a single statement is supported per request. It cannot operate within a context (e.g., Patient) and will not execute correctly if input parameters are needed.
`subject`	✅	`string`	Only Patient references are supported.
`parameters`	✅	`Parameters` resource	Input parameters passed into the evaluation context. These will be mapped from FHIR data types to CQL data types according to the FHIR Type Mapping.
`library`	❌	Complex
`useServerData`	❌	`boolean`
`data`	❌	`Bundle`
`prefetchData`	❌	Complex
`dataEndpoint`	❌	`Endpoint` resource
`contentEndpoint`	❌	`Endpoint` resource
`terminologyEndpoint`	❌	`Endpoint` resource
`raw`	✅	`boolean`	Return the execution results as a string without mapping the CQL result data types back to FHIR. This is a proprietary parameter of Firely Server.

Example: System-Level $cql Invocation

This examples demonstrates a simple calculation executed via the dQM engine.

Request

POST [base]/$cql HTTP/1.1
Content-Type: application/fhir+json

Request Body

 {
  "resourceType": "Parameters",
  "parameter": [
      {
          "name": "expression",
          "valueString": "'Hello'&' '&'World'"
      }
  ]
}

Response Body

 {
  "resourceType": "Parameters",
  "parameter": [
      {
          "extension": [
              {
                  "url": "http://hl7.org/fhir/StructureDefinition/cqf-cqlType",
                  "valueString": "String"
              }
          ],
          "name": "return",
          "valueString": "Hello World"
      }
  ]
}