### Must support
The meaning of the presence or absence of the must support flag is described in [Must support](guidance.html#must-support).

### Usage notes

#### Server validation rules
In addition to the invariants defined in this profile, *value[x].start* and *value[x].end* elements must meet the following validation rules which are applied by the [PCA Publisher Agent](CapabilityStatement-pca-publisher-agent.html) FHIR API:
 * The *value[x].start* element shall be equal to, or earlier than, the *period.start* or *period.end* values of any practitioner role resources that reference this healthcare service.
 * The *value[x].end* element shall be equal to, or later than, the *period.start* or *period.end* values of any practitioner role resources that reference this healthcare service.
