Reference Architecture
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Reference Architecture, published by WHO. This guide is not an authorized publication; it is the continuous build for version 0.2.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/costateixeira/smart-ra/tree/glossary and changes regularly. See the Directory of published versions

Methodology

Methodology

One of the core principles guiding this architecture is that architecture SHALL be accessible to stakeholders.

This means:

  • Business Architecture must be readable and understandable by business leaders and domain experts.
  • Stakeholders should not need prior knowledge of technical frameworks like TOGAF or specific modeling languages to engage with the architectural content.

To support this, we emphasize:

  • Plain-language definitions
  • Layered explanations, separating business intent from technical implementation
  • Clear, consistent diagrams, with minimal jargon

Structure and Maintainability

While accessibility is essential, so is discipline.

Architectural descriptions must be:

  • Structured: Organized by consistent concepts (goals, capabilities, components, services)
  • Maintainable: Designed to evolve as the enterprise changes
  • Machine-readable: Where possible, enabling reuse, validation, and integration
  • Coherent: Diagrams and text should form a unified model, not scattered or contradictory fragments

To achieve this, we use:

  • TOGAF as a conceptual framework for organizing architectural domains and layers
  • ArchiMate notation (via PlantUML) for visual modeling
  • A structured substrate: defined concepts (e.g., Goal, Capability, Application Component) are reused across views
  • FHIR (HL7 Fast Healthcare Interoperability Resources) for aligning with healthcare data standards and integrating architectural elements into real-world systems

Integration with Standards

This architecture connects directly to healthcare interoperability standards, enabling it to be:

  • Semantic: Using FHIR resources and vocabularies for consistency with health data models
  • Pragmatic: Able to inform and validate system implementation
  • Extensible: Supporting layered architectures that evolve with health system needs

We use FHIR not just for data modeling, but also to link architecture elements (e.g., client registry capability → Patient resource → integration profiles like IHE PIXm).

Summary

This methodology balances clarity for stakeholders with rigor for implementers.

  • Readers should be able to understand what the architecture means.
  • Designers should be able to trace why a component exists and how it connects.
  • Tools should be able to analyze, validate, and extend the model.

By grounding our work in TOGAF, ArchiMate, and FHIR, we ensure our architecture is:

  • Understandable
  • Maintainable
  • Standardized
  • Connected to real-world health IT