| id | 0..1 | string | Logical id of this artifact |
| meta | 0..1 | Meta | Metadata about the resource |
| implicitRules | 0..1 | uri | A set of rules under which this content was created |
| language | 0..1 | code | Language of the resource content |
| text | 0..1 | Narrative | Text summary of the resource, for human interpretation |
| contained | 0..* | Resource | Contained, inline Resources |
| extension | 0..* | Extension | Additional content defined by implementations |
| modifierExtension | 0..* | Extension | Extensions that cannot be ignored |
| identifier | 0..* | Identifier | Unique identifier |
| instantiatesCanonical | 0..* | canonical | Instantiates FHIR protocol or definition |
| instantiatesUri | 0..* | uri | Instantiates external protocol or definition |
| basedOn | 0..* | Reference | Request fulfilled by this communication |
| partOf | 0..* | Reference | Part of this action |
| inResponseTo | 0..* | Reference | Reply to |
| status | 1..1 | code | preparation | in-progress | not-done | on-hold | stopped | completed | entered-in-error | unknown |
| statusReason | 0..1 | CodeableConcept | Reason for current status |
| category | 0..* | CodeableConcept | Message category |
| priority | 0..1 | code | routine | urgent | asap | stat |
| medium | 0..* | CodeableConcept | A channel of communication |
| subject | 0..1 | Reference | Focus of message |
| topic | 0..1 | CodeableConcept | Description of the purpose/content |
| about | 0..* | Reference | Resources that pertain to this communication |
| encounter | 0..1 | Reference | Encounter created as part of |
| sent | 0..1 | dateTime | When sent |
| received | 0..1 | dateTime | When received |
| recipient | 0..* | Reference | Message recipient |
| sender | 0..1 | Reference | Message sender |
| reasonCode | 0..* | CodeableConcept | Indication for message |
| reasonReference | 0..* | Reference | Why was communication done? |
| payload | 0..* | BackboneElement | Message payload |
| note | 0..* | Annotation | Comments made about the communication |