Webapi

Reference notes on OMOP’s standard-concept mapping, one level below the usual explanation. For why OMOP forces everything through standard concepts in the first place, see Michael Wornow’s STARR-OMOP post, which walks the same ICD-9 → SNOMED example (427.31 → 313217) via concept_relationship. The question these notes answer: given a non-standard OMOP concept, which standard concept does it actually resolve to, does that standard concept have any patients in this data, and how do you find out, concretely, at the level of the exact tables, one real row, and the actual WebAPI SQL/JSON? ...

When I started working with OHDSI WebAPI to build a research data platform, one of the first things that required a genuine shift in thinking was the relationship between cohort definitions, cohort generations, and cohort characterizations. OHDSI separates these into distinct concepts with independent lifecycles — a design that reflects the realities of large-scale observational research: multi-source execution, longitudinal re-runs, and full reproducibility requirements. Once you internalize why the separation exists, the WebAPI endpoint structure starts to feel very intentional. ...