Create a FHIR Group resource to define an attributed patient cohort for bulk data operations

Verified steps

1. Determine the Group type appropriate for your use case: for patient cohorts, set Group.type to 'person' and Group.actual to true (for an enumerated list of known members) or false (for a definitional/characteristic-based group).
2. For an enumerated Group, populate Group.member with references to each Patient resource in the cohort; include Group.member.period if attribution is time-bound and Group.member.inactive to flag members who have left the cohort.
3. For a characteristic-based Group, define Group.characteristic elements to describe the cohort criteria (e.g., patients attributed to a specific practitioner, patients with a specific condition); note that not all FHIR servers support characteristic-based Group evaluation.
4. POST the Group resource to [base]/Group and record the assigned id; this id will be used as the target for group-level $export operations.
5. Maintain Group membership as attribution changes: use PATCH or PUT to update Group.member entries, marking departed members as inactive rather than deleting them to preserve historical attribution records.
6. Reference the Group resource in value-based care workflows (Da Vinci ATR), bulk export operations ([base]/Group/[id]/$export), and quality measure reporting.