SDC-Template-based Extract

A Typescript reference implementation of the $extract operation from the HL7 FHIR Structured Data Capture Specification. This only covers template-based extraction.

Usage

There are two ways to use this package:

1. Using it in a web app
2. Using it in a backend service e.g. ExpressJS

Using it in a web app

It is recommended to use inAppExtraction(), which performs an in-app extraction. This means that the app is not sending data to an external server, but rather using JavaScript to perform the extraction in the browser.

const responseToExtract = structuredClone(savedResponse); // Good practice to deep clone the response to prevent mutating the original response
const inAppExtractOutput = await inAppExtract(
  responseToExtract,
  sourceQuestionnaire
);

const { extractResult, extractSuccess } = inAppExtractOutput;

// Extraction is successful
if (extractSuccess && !extractResultIsOperationOutcome(extractResult)) {
  const extractedBundle = extractResult.extractedBundle;

  // Do things with the successfully extracted transaction bundle...
}

Available parameters for inAppExtract():

| Parameter | Description | |-------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | questionnaireResponse | QuestionnaireResponse to extract data from | | questionnaireOrCallback | Either a Questionnaire resource or a fetch/callback configuration for dynamic retrieval (if module making the inAppExtract() call does not have access to the Questionnaire resource). | | comparisonSourceResponse | An optional QuestionnaireResponse used for comparison when extracting. If this is provided, only "modified" items will be extracted. In most cases, this likely is the pre-populated response. |

Using it in a backend service

Using this library in a backend service requires more pre-configuration. Due to how the $extract works, you will need to provide a Parameters resource defining the input parameters conforming to the extract() function.

sdc-template-extract allows you to specify custom questionnaire and comparison-source-response parameters, allowing you to pass their respective resources directly to the extract() function. A library function createInputParameters() is provided to help you create the Parameters resource.

There is no sample implementation of using the extract() function in a backend service as of now.

Local development notes

It's recommended to run this library within a web app or a service if you're doing local development. This library compiles to both CommonJS and ES Modules, so there is no problems in using it across web frameworks and Node-based backends.

To compile the code, use npm run compile. To watch for changes, use npm run watch.

Note: Do not use tsc or tsc -w as it will only compile to ES Modules, which means it will not work with CommonJS-based implementations.