has_part has part has part one-dimensional temporal region observation period In OMOP, the observation table contains records that defines spans of time during which two conditions are expected to hold: (i) Clinical Events that happened to the Person are recorded in the Event tables, and (ii) absense of records indicate such Events did not occur during this span of time. Oliver He, Long Tran https://ohdsi.github.io/CommonDataModel/cdm60.html#OBSERVATION_PERIOD participant observation duration time EUPATH_0000138 A period time when an observation is conducted. observation temporal region observation period start date observation period end date