OHDSI Conventions
The OMOP Common Data Model (CDM) is a standardized data model maintained by the OHDSI community. It provides a common structure for storing and analyzing healthcare data from diverse sources, enabling large-scale observational studies and federated research across institutions.
The OHDSI conventions are guidelines and best practices for implementing the CDM — covering data types, vocabulary usage, domain routing, and transformation processes. These conventions ensure that OHDSI tools (ATLAS, HADES, CohortDiagnostics) work consistently across all sites.
Key Resources
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CDM Documentation
The official specification for the OMOP CDM. Emory uses version 5.4.
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General Conventions
Rules for data types, null handling, date formats, and standard field behaviors across all CDM tables.
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THEMIS Convention Library
Community-ratified conventions for specific data scenarios — the authoritative source for "how should this be modeled?"
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OHDSI Forums
Active community discussions on CDM best practices, edge cases, and evolving conventions not yet codified in THEMIS.
Dataset-Specific Conventions
Conventions for specific data types or patient groups are developed by OHDSI workgroups. Common examples include:
- Healthcare Systems Interest Group — conventions for healthcare system data
- Oncology Workgroup — conventions for patient oncology data
These workgroups publish conventions as white papers or technical reports, available on the OHDSI website or through academic publications.
Emory's Adherence
Emory follows the General and THEMIS conventions to the extent known as of April 2025. There are known convention adherence gaps due to team workload — see Convention Adherence for details.