| url | No | uri | Canonical identifier for this research element definition, represented as a URI (globally unique) |
| identifier | No | Identifier[] | Additional identifier for the research element definition |
| version | No | string | Business version of the research element definition |
| name | No | string | Name for this research element definition (computer friendly) |
| title | No | string | Name for this research element definition (human friendly) |
| shortTitle | No | string | Title for use in informal contexts |
| subtitle | No | string | Subordinate title of the ResearchElementDefinition |
| status | Yes | code | draft / active / retired / unknown |
| experimental | No | boolean | For testing purposes, not real usage |
| subject[x] | No | CodeableConcept, Reference<Group> | E.g. Patient, Practitioner, RelatedPerson, Organization, Location, Device |
| date | No | dateTime | Date last changed |
| publisher | No | string | Name of the publisher (organization or individual) |
| contact | No | ContactDetail[] | Contact details for the publisher |
| description | No | markdown | Natural language description of the research element definition |
| comment | No | string[] | Used for footnotes or explanatory notes |
| useContext | No | UsageContext[] | The context that the content is intended to support |
| jurisdiction | No | CodeableConcept[] | Intended jurisdiction for research element definition (if applicable) |
| purpose | No | markdown | Why this research element definition is defined |
| usage | No | string | Describes the clinical usage of the ResearchElementDefinition |
| copyright | No | markdown | Use and/or publishing restrictions |
| approvalDate | No | date | When the research element definition was approved by publisher |
| lastReviewDate | No | date | When the research element definition was last reviewed |
| effectivePeriod | No | Period | When the research element definition is expected to be used |
| topic | No | CodeableConcept[] | The category of the ResearchElementDefinition, such as Education, Treatment, Assessment, etc. |
| author | No | ContactDetail[] | Who authored the content |
| editor | No | ContactDetail[] | Who edited the content |
| reviewer | No | ContactDetail[] | Who reviewed the content |
| endorser | No | ContactDetail[] | Who endorsed the content |
| relatedArtifact | No | RelatedArtifact[] | Additional documentation, citations, etc. |
| library | No | canonical[] | Logic used by the ResearchElementDefinition |
| type | Yes | code | population / exposure / outcome |
| variableType | No | code | dichotomous / continuous / descriptive |
| characteristic | Yes | ResearchElementDefinitionCharacteristic | What defines the members of the research element |
| - id | No | string | Unique id for inter-element referencing |
| - extension | No | Extension[] | Additional content defined by implementations |
| - modifierExtension | No | Extension[] | Extensions that cannot be ignored even if unrecognized |
| - definition[x] | Yes | CodeableConcept, canonical, Expression, DataRequirement | What code or expression defines members? |
| - usageContext | No | UsageContext[] | What code/value pairs define members? |
| - exclude | No | boolean | Whether the characteristic includes or excludes members |
| - unitOfMeasure | No | CodeableConcept | What unit is the outcome described in? |
| - studyEffectiveDescription | No | string | What time period does the study cover |
| - studyEffective[x] | No | dateTime, Period, Duration, Timing | What time period does the study cover |
| - studyEffectiveTimeFromStart | No | Duration | Observation time from study start |
| - studyEffectiveGroupMeasure | No | code | mean / median / mean-of-mean / mean-of-median / median-of-mean / median-of-median |
| - participantEffectiveDescription | No | string | What time period do participants cover |
| - participantEffective[x] | No | dateTime, Period, Duration, Timing | What time period do participants cover |
| - participantEffectiveTimeFromStart | No | Duration | Observation time from study start |
| - participantEffectiveGroupMeasure | No | code | mean / median / mean-of-mean / mean-of-median / median-of-mean / median-of-median |
