CAIRN

Clinical interoperability reference architecture. Built on FM-2.

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⚠️ CAIRN is NOT a medical device as defined by EU MDR 2017/745, EU IVDR 2017/746, or MPDG. It is a mathematical framework for research and interoperability validation only. It does not process real patient data in production contexts.

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What is CAIRN?

CAIRN is an open-source reference architecture for formal verification of clinical interoperability mappings. It implements FM-2 — a mathematical framework modelling clinical data through:

• a type system as a directed acyclic graph (DAG)
• Allen temporal algebra (13 interval relations)
• a universal event model as a 6-tuple: (id, type, temporal, value_set, context, provenance)
• Z3 SMT proofs for value-space containment and structural preservation
• SILD (Silent Information Loss Detector) for CDR-to-FHIR mapping verification

CAIRN answers a practical question:

What is silently lost when clinical data moves from one system to another — and how can we prove it formally, before production?

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Was ist CAIRN?

CAIRN ist eine offene Referenzarchitektur für die formale Verifikation klinischer Interoperabilitäts-Mappings. Sie implementiert FM-2 — ein mathematisches Modell klinischer Daten auf Basis von:

• einem Typsystem als gerichtetem azyklischen Graphen (DAG)
• Allen-Temporalalgebra (13 Intervallrelationen)
• einem universellen Ereignismodell als 6-Tupel: (id, type, temporal, value_set, context, provenance)
• Z3 SMT-Beweisen für Werteraum-Containment und Strukturerhalt
• SILD (Silent Information Loss Detector) zur CDR-zu-FHIR-Verifikation

Was geht beim Datentransfer zwischen klinischen Systemen still verloren — und wie lässt sich das formal nachweisen, bevor es in Produktion geht?

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Real-World Loss Patterns Detected by CAIRN

Loss Class	Clinical Example	FM-2 Formalism	SILD Class
Temporal precision	Anaesthesia 08:12–11:47 → 00:00–23:59	Allen: DURING	REGRESSION
Negation absence	"No known allergy" → empty FHIR Bundle	Cardinality n→0	SILENT_LOSS
Terminology drift	SNOMED laterality → ICD-10-GM (lost)	Value-space ⊊	DRIFT
HL7 field mapping	Cholesterol ref. range + "H" flag dropped	Z3: not surjective	PERSISTENT
Cardinality collapse	4 CDR diagnoses → 2 FHIR diagnoses	φ_B: CDR ≠ FHIR	REGRESSION

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Quickstart

pip install cairn-clinical

from cairn.adapters import FHIRAdapter
from cairn.verification import SILDAnalyzer

# Load CDR source and FHIR target
adapter     = FHIRAdapter()
cdr_events  = adapter.load_bundle_file("source_cdr.json")
fhir_events = adapter.load_bundle_file("mapped_fhir.json")

# Detect silent information loss
report = SILDAnalyzer().compare(cdr_events, fhir_events)
report.print_summary()

════════════════════════════════════════════════════════════════
 CAIRN / SILD Report  —  2026-05-25 09:00
════════════════════════════════════════════════════════════════
 Source : CDR  (5 events)
 Target : FHIR-R4  (3 events)
────────────────────────────────────────────────────────────────
 [SILENT_LOSS|CRITICAL] AllergyStatement/716186003: Negated event absent in FHIR
 [REGRESSION|HIGH]      Anaesthesia/72641008: Temporal precision lost (215min → 1439min)
 [DRIFT|HIGH]           TerminologyDrift/416098002: SNOMED laterality → ICD-10-GM (lost)
 [REGRESSION|MEDIUM]    LabResult/2093-3: Value-space not preserved: missing referenceRange
────────────────────────────────────────────────────────────────
 Total: 4 findings | 2 regressions | 1 silent losses | 1 critical
════════════════════════════════════════════════════════════════

# CLI
cairn verify   --source cdr.json  --target fhir.json  --output report.json
cairn drift    --source cdr.json  --target fhir.json
cairn variance --files a.csv:HausA:Orbis  --files b.csv:HausB:iMedOne
cairn version

Version comparison (IMPROVEMENT detection)

# Compare two mapping versions — detect improvements and regressions
report_v1 = SILDAnalyzer().compare(cdr_events, fhir_v1_events, mapping_version="1.0")
report_v2 = SILDAnalyzer().compare(cdr_events, fhir_v2_events, mapping_version="2.0",
                                    reference_report=report_v1)
# IMPROVEMENT findings mark event codes resolved since v1
report_v2.print_summary()

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Modules

Module	Contents
cairn.core	Type DAG · Allen algebra (13 relations) · 6-tuple event model · Homomorphism checker
cairn.verification	Z3 SMT proofs · Value-space containment · SILD engine (all 6 classifications)
cairn.adapters	FHIR R4 · HL7 v2 (ORU/ADT/RXA) · CSV/DataFrame
cairn.analysis	Cohort queries φA–φD · Terminology drift (8 system pairs) · Multi-site KIS variance
cairn.api	FastAPI REST (POST /verify · POST /drift · GET /health)
cairn.cli	Click CLI (verify · drift · variance · version)

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Architecture

cairn/
├── core/
│   ├── allen.py          # Allen temporal algebra — 13 interval relations
│   ├── event.py          # Universal event model — 6-tuple (FMEvent)
│   ├── homomorphism.py   # Structure-preservation checker
│   └── type_dag.py       # Type system as directed acyclic graph
│
├── verification/
│   ├── sild.py           # Silent Information Loss Detector (SILD)
│   └── z3_proofs.py      # Z3 SMT formal proofs
│
├── adapters/
│   ├── csv_df.py         # CSV / pandas DataFrame
│   ├── fhir_r4.py        # FHIR R4 (Observation, Condition, Procedure, ...)
│   └── hl7v2.py          # HL7 v2 (ORU^R01, ADT^A01, RXA)
│
├── analysis/
│   ├── cohort.py         # FM-2 cohort queries φA–φD
│   ├── terminology.py    # Terminology drift checker (8 system-pair mappings)
│   └── variance.py       # Multi-site completeness variance (KIS comparison)
│
├── api/
│   └── app.py            # FastAPI REST API
│
└── cli/
    └── commands.py       # Click command-line interface

tests/
├── unit/                 # FM-2 core + CLI + API (32 tests)
├── integration/          # SILD — all 5 real-world loss patterns + drift (8 tests)
└── property/             # Hypothesis property tests — FM-2 invariants P1–P6

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Dependencies

CAIRN is built exclusively on publicly available PyPI libraries. All dependencies with their licences are documented in NOTICE.

# Core
networkx       >= 3.2    # Type DAG, homomorphism       BSD-3-Clause
z3-solver      >= 4.12   # SMT formal verification       MIT
pydantic       >= 2.5    # Schema validation             MIT
pandas         >= 2.1    # DataFrame adapter             BSD-3-Clause

# Healthcare standards
fhir.resources >= 7.1    # FHIR R4                      BSD-3-Clause
hl7            >= 0.4    # HL7 v2 parsing               BSD-3-Clause

# API & CLI
fastapi        >= 0.110  # REST API                      MIT
httpx          >= 0.27   # API test client               BSD-3-Clause
click          >= 8.1    # CLI                           BSD-3-Clause

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Tests

pip install -e ".[dev]"
pytest tests/ -v

50 passed in 3.16s

tests/unit/        32 tests  (Type DAG · Allen algebra · event model · CLI · API)
tests/integration/  8 tests  (5 SILD loss patterns + terminology drift)
tests/property/     6 tests  (Hypothesis: FM-2 invariants P1–P6)

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Licence

CAIRN is licensed under the GNU Affero General Public License v3 (AGPL-3.0-only OR Commercial).

• Free to use, modify, and distribute
• Modifications must be contributed back under the same licence
• Copyleft covers network use (SaaS)
• Legally valid in all EU member states in their official languages

See LICENCE for the full text.

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Not a Medical Device

CAIRN is a mathematical research tool. It is not a medical device under:

• EU MDR 2017/745 (Medical Device Regulation)
• EU IVDR 2017/746 (In Vitro Diagnostic Regulation)
• MPDG — Medizinprodukterecht-Durchführungsgesetz (Deutschland)

See NOTICE for the complete disclaimer.

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Related Projects

Project	Description	DOI / Link
FM-1	Grundlagen zur wissenschaftlichen Auswertung von klinischen Informationen	10.5281/zenodo.19205557
FM-4 / SILD	Signal-Loss Inspection at Data-boundaries — Theoriepaper zu CAIRN	10.5281/zenodo.20375435
SILD Stack	FM-4 konformer Monitoring-Stack (HL7 v2 · FHIR R4 · Prometheus · Grafana)	github.com/fmatten/SILD
AION	FM-3: Algebraic Interval Ontology for Clinical Networks	github.com/fmatten/aion · codeberg.org/iscad/aion · 10.5281/zenodo.19553130

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Contributing

Contributions are welcome under AGPL-3.0 OR Commercial. By contributing, you agree your changes will be returned to the reference system.

• Issues: https://github.com/fmatten/CAIRN/issues
• Mirror: https://codeberg.org/iscad/cairn
• Guide: CONTRIBUTING.md

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Citation

@software{cairn2026,
  title   = {CAIRN — Clinical interoperability reference architecture},
  author  = {Matten, Friedhelm},
  year    = {2026},
  doi     = {10.5281/zenodo.20375036},
  url     = {https://github.com/fmatten/CAIRN},
  licence = {AGPL-3.0-only},
  version = {1.0.1}
}