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cdisc-org / DDF-RA

This is the repository for all code and documentation for the DDF-RA project.
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Update cardinality for `StudyDesign` `population` relationship #430

Open ASL-rmarshall opened 3 months ago

ASL-rmarshall commented 3 months ago

The cardinality for the StudyDesign.population relationship is currently 0..1, which implies that specifying a population for the study design is optional. I think the cardinality should be changed to 1 to indicate that a population must always be specified for a study design.

ASL-rmarshall commented 3 months ago

If it's true that a population must always be specified for a study design, do we need a USDM v3.0 rule to enforce this requirement?

Note that the rule created for check CHK0190 (DDF00050) - study arms must only reference study cohorts that are defined within the population defined within the same study design as the study arm - relies on a population being defined for the study design.

ASL-rmarshall commented 3 months ago

Currently (as of release 3.4), the StudyDesign.population relationship is a "definitional" relationship in the API specification - the definition of the StudyDesignPopulation is included within the StudyDesign; the StudyDesignPopulation is not referenced by id. Similarly, the StudyDesignPopulation.cohorts relationship is also "definitional" - study cohorts can only be defined within the context of a StudyDesignPopulation.

What happens if you have 2 study designs that use different cohorts of the same population?

At the moment, you'd have to duplicate the population definition in the 2 study designs so that the study-design-specific cohort definitions can be defined within the relevant study design. If the population/cohort definitions were moved to a (n API only) collection under StudyVersion (in the same way that EligibilityCriterion definitions have been moved), it would be possible to create a single population definition (containing definitions for all the cohorts that are needed) and then to reference the population and relevant cohorts by id.