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Preprocessor

A Preprocessor is a pluggable service that semantically annotates raw ePIs using standard terminologies (like SNOMED-CT or ICPC-2) to generate a Preprocessed ePI (p(ePI)).

Purpose​

Preprocessors transform raw ePI into p(ePI) by:

  • Reading ePI narrative text
  • Identifying medically relevant sections
  • Annotating with standard terminology codes
  • Embedding annotations as HTML class attributes

Technical Implementation​

Required Endpoint​

Must implement /preprocess REST endpoint:

  • Input: ePI Bundle (FHIR JSON)
  • Output: p(ePI) Bundle (FHIR JSON)
  • Specification: OpenAPI definition

Service Discovery​

Must be deployed with Kubernetes label:

eu.gravitate-health.fosps.preprocessing=true

This enables Focusing Manager auto-discovery.

Containerization​

  • Packaged as Docker containers
  • Deployed via Kubernetes
  • Language/framework agnostic

Annotation Mechanism​

Preprocessors add HtmlElementLink extensions to the Composition:

{
  "extension": [{
    "url": "elementClass",
    "valueString": "pregnancy-warning"
  }, {
    "url": "concept",
    "valueCodeableConcept": {
      "coding": [{
        "system": "http://snomed.info/sct",
        "code": "77386006"
      }]
    }
  }]
}

2. Modify HTML Narrative​

Add class attributes to HTML tags in Composition.text.div:

<p class="pregnancy-warning">
  Do not use during pregnancy.
</p>

Stacking Support​

Preprocessors must handle stacking:

  • Input may already be p(ePI) from previous preprocessor
  • Avoid duplicate annotations
  • Append to existing class attributes (don't nest tags)
  • Check for existing HtmlElementLink extensions

HTML Modification Rules​

Allowed:

  • Adding HTML class attributes
  • Wrapping text in <span> tags
  • Adding classes to existing tags (<p>, <h1>, <li>, etc.)

Prohibited:

  • Removing content
  • Changing narrative text
  • Deleting HTML elements
  • Modifying approved wording

Performance Considerations​

Preprocessors should handle:

  • Heavy computation: NLP models, semantic analysis
  • Slow operations: External API calls, database lookups

This allows Lenses to remain lightweight and fast.