Architecture
Architecture is the set of decisions that are expensive to reverse. In digital health that usually means identifiers, terminology, the exchange model and the governance around them — not the choice of programming language or cloud provider, which teams tend to argue about far more.
This section covers how to describe a health system before building it, which frameworks help, and how to record the decisions so that the next team understands why the system looks the way it does.
The layers
Every serious architecture description separates these concerns. The names vary between frameworks; the separation does not.
| Layer | Question it answers | Typical artefacts |
|---|---|---|
| Business | What health outcomes are we accountable for, and for whom? | Service catalogue, stakeholder map, outcome measures |
| Capability | What must the system be able to do, independent of software? | Capability model, maturity assessment |
| Process | How does the work actually flow? | BPMN workflows, Digital Adaptation Kits |
| Information | What do we mean by "patient", "encounter", "facility"? | Conceptual model, glossary, registries |
| Data | How is that represented, stored, and moved? | Logical and physical models, FHIR profiles |
| Application | Which systems provide which capabilities? | Application portfolio, platforms |
| Integration | How do systems talk? | Interoperability layer, APIs, events |
| Technology | What does it run on? | Infrastructure, deployment topology |
| Security | Who may do what, and how is that proven? | Security architecture, threat model |
| Governance | Who decides, and how do decisions change? | Governance, architecture review board |
The order that works
The common failure is to start at the technology layer because it is the most tractable. A country buys an interoperability layer, then discovers it has no agreed patient identifier, no facility list anyone trusts and no legal basis for sharing data — so the layer routes messages nobody can act on.
A more reliable order:
1. Name the health problem "Women are lost to follow-up between ANC visits"
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2. Identify the capability "Continuity of the maternal record across facilities"
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3. Model the workflow Who does what, where, in what order
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4. Decide the information model What is a "pregnancy episode"? Which identifier?
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5. Choose standards FHIR profiles, terminology bindings
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6. Design the exchange Which pattern — central, federated, hybrid?
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7. Select or build applications EMR, CHW app, HMIS
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8. Infrastructure and operations Hosting, availability, monitoring
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9. Security, consent, governance Not a final step — a constraint on all of the above
Step 9 is written last only because it constrains everything above it. It is started first.
Reference architecture versus solution architecture
These are different documents and confusing them wastes months.
| Reference architecture | Solution architecture | |
|---|---|---|
| Scope | A class of systems | One system, one context |
| Names technologies? | Rarely — it names components | Yes, specifically |
| Owned by | The ecosystem (a ministry, a community) | The implementing team |
| Changes | Slowly, by consensus | Per release |
| Example | OpenHIE, WHO Digital Health Platform | "The ANC module deployed on OpenMRS 3 in Province 2" |
A reference architecture that names vendors has stopped being one. A solution architecture that names none is not yet a plan.
Use the reference architecture template for the former.
In this section
- Digital health architecture — the layered reference model
- Architecture frameworks — which framework does what, and which ones are health-specific
- Enterprise architecture — business, capability and process architecture applied to health
- C4 model — describing a system at four levels of zoom
- Architecture decision records — writing decisions down so they survive staff turnover
- Architecture patterns — the reusable pattern catalogue
- Maturity model — assessing where an ecosystem is
References
- OpenHIE architecture specification — https://ohie.org/
- WHO, Digital Implementation Investment Guide — https://www.who.int/publications/i/item/9789240010567
- The Open Group, TOGAF Standard — https://www.opengroup.org/togaf