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Healthcare Data,
Explained from First Principles

Deep-dive guides on Epic, Cerner, FHIR, and the data models behind every EHR. Written for clinicians who want to understand the systems they use — and analysts who want to understand the medicine behind the data.

The Universal Healthcare Data Chain — referenced in every article below
Patient / EPT / Person → Encounter / CSN / encntr_id → Clinical Event / FLO / DTA → Data Point / FSD / clinical_event → Who + When + Value
Articles & Guides

From zero to informed

No vendor marketing. No surface-level overviews. Each guide explains the why, not just the what.

● Live
01 · Epic Data Architecture
How Epic Actually Stores Your Data
Chronicles, Clarity, and Caboodle explained. The FLO → FSD → CSN → EPT chain. Why there's a ~24-hour lag in your Reporting Workbench reports. What INI master files are and why every clinical data point has one.
Chronicles Clarity Caboodle ETL Core concept
◌ Coming Soon
02 · Interoperability History
The 40-Year Fight for Healthcare Data Standards
Why did it take a $25.9 billion federal law to make hospitals use electronic records? The story of Dr. Don Simborg, HL7, HIPAA, HITECH, Meaningful Use, FHIR, and the 21st Century Cures Act.
HL7 HITECH FHIR Don Simborg Essential history
◌ Coming Soon
03 · Epic vs Cerner Crosswalk
Same Structure, Different Language
EPT is a Person. CSN is an encntr_id. FLO is a DTA. FSD is a clinical_event row. Both systems arrived at the same data model independently — here's exactly how the terminology maps, concept by concept.
DTA Event Code Millennium Crosswalk
◌ Coming Soon
04 · Analytics Tools Explained
SlicerDicer vs Reporting Workbench vs Radar
Three tools in the same Analytics Catalog, three different data sources, three different jobs. The ~24hr lag, real-time Chronicles queries, and when to use which tool — without writing a line of SQL.
SlicerDicer RWB Cogito End user guide
Quick Reference

Epic · Cerner · FHIR Crosswalk

The same data model, three vocabularies. Every major concept mapped across all three systems.

Concept Epic Term Cerner Term FHIR Resource What It Represents
Patient EPT (Master Patient) Person / PAT_PERSON Patient The human being. Root anchor for all clinical data.
Encounter / Visit CSN (Contact Serial Number) encntr_id Encounter A single visit, admission, or contact episode. Every clinical event must tie to one.
Flowsheet Template FLO (Flowsheet Row) DTA (Discrete Task Assay) ObservationDefinition The definition of a measurable item — "Heart Rate", "SpO2", "GCS Score".
Flowsheet Value FSD (Flowsheet Data) clinical_event Observation The actual recorded value with timestamp, clinician, and encounter context.
Order ORD / Order ID order_id ServiceRequest / MedicationRequest A clinician's request for a medication, lab, procedure, or referral.
Order Result RSH (Result) clinical_event (result type) Observation / DiagnosticReport The output of a completed order — lab values, imaging reads, procedure notes.
Problem PRL (Problem List) PROBLEM_LIST Condition Active or resolved diagnoses maintained across encounters.
Medication Admin MAR (Medication Administration Record) CE_MED_RESULT MedicationAdministration What was actually given to the patient, by whom, at what time and dose.
Master File INI (Item/Master File) Code Set / Nomenclature CodeSystem / ValueSet Lookup tables that define valid values across the system (medication names, procedure codes, etc).
Reporting Database Clarity (SQL) / Caboodle (EDW) CCL / HealtheAnalytics SMART on FHIR / Bulk API The analytics copy of the operational EHR data (~24hr ETL lag for Clarity).
Glossary

Key terms, plain English

The vocabulary that never gets explained in training materials.

Chronicles
Epic · Operational Database
Epic's live operational database. Uses a proprietary cache-based NoSQL-style storage. Real-time but not directly queryable with standard SQL by most users.
→ FHIR: raw source behind all FHIR endpoints
Clarity
Epic · Reporting Database
A SQL-queryable relational copy of Chronicles. Populated by an ETL process that typically runs nightly — creating the famous ~24-hour lag in reports.
→ Analogous to: Cerner CCL database
Caboodle
Epic · Data Warehouse
Epic's enterprise data warehouse (EDW). Dimensional model built on top of Clarity for analytics and population health reporting. Powers SlicerDicer.
→ Analogous to: Cerner HealtheAnalytics
EPT
Epic · Master Patient Record
The master patient INI in Epic. Every patient has a single EPT record that persists forever and anchors all encounter and clinical data.
→ FHIR: Patient resource
CSN
Epic · Contact Serial Number
A unique, permanent identifier for a single patient contact (visit, admission, call). Once assigned, a CSN never changes or gets reused — it's the anchor for all encounter-level data.
→ FHIR: Encounter.id
FLO / FSD
Epic · Flowsheet System
FLO is the flowsheet row definition (the "what" — e.g., Heart Rate). FSD is the actual recorded value (the "what happened"). FSD rows have CSN and EPT foreign keys.
→ FHIR: ObservationDefinition + Observation
DTA
Cerner · Discrete Task Assay
Cerner's equivalent of a FLO row — the master definition of a discrete, measurable clinical item. Every charted value links back to a DTA record.
→ FHIR: ObservationDefinition
clinical_event
Cerner · Core Results Table
The single largest table in Cerner's database. Stores every charted value, lab result, and order result with event_cd (what was measured), event_end_dt_tm (timestamp), and encntr_id (encounter).
→ FHIR: Observation + DiagnosticReport
INI
Epic · Master File Type
Every type of record in Epic (patient, encounter, order, result) is stored in an INI — a named master file. EPT, CSN, FLO, ORD are all INI types. Understanding INIs is understanding how Epic is structured.
→ FHIR: Resource type definitions
SlicerDicer
Epic · Self-Service Analytics
Epic's self-service reporting tool for end users. Queries Caboodle (the data warehouse), so data reflects the ~24hr lag. Powerful but has limits for complex multi-table joins.
→ No FHIR equivalent
Reporting Workbench
Epic · Analyst Reporting
Epic's analyst-level reporting tool. Queries Clarity (the SQL replica), allowing complex joins but still with the ~24hr ETL lag. More flexible than SlicerDicer.
→ No FHIR equivalent
FHIR
HL7 · Interoperability Standard
Fast Healthcare Interoperability Resources (2012). The modern standard for exchanging healthcare data via RESTful APIs. Defines 145+ resource types that map directly to the Patient → Encounter → Observation chain.
→ Implemented by both Epic and Cerner