Global
global-1: All FHIR elements must have a @value or children
Bundle
bdl-2: entry.search only when a search
bdl-1: total only when a search or history
bdl-7: FullUrl must be unique in a bundle, or else entries with the same fullUrl must have different meta.versionId
bdl-3: entry.request only for some types of bundles
bdl-4: entry.response only for some types of bundles
bdl-5: must be a resource unless there's a request or response
bdl-6: The fullUrl element must be present when a resource is present, and not present otherwise
ref-1: SHALL have a local reference if the resource is provided inline