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5.7 Resource CompartmentDefinition - Content

FHIR Infrastructure icon Work GroupMaturity Level: 3 Trial UseSecurity Category: Anonymous Compartments: No defined compartments

A compartment definition that defines how resources are accessed on a server.

5.7.1 Scope and Usage

Each resource may belong to one or more logical compartments. A compartment is a logical grouping of resources which share a common property. Compartments have two principal roles:

  • Function as an access mechanism for finding a set of related resources quickly
  • Provide a definitional basis for applying access control to resources quickly

Notes:

  • At present, compartment definitions can only be defined by HL7 International. This is because their existence creates significant impact on the behavior of servers.
  • Although compartment definitions can be a useful foundation for access control, they may not be sufficient for this purpose. Resources outside the compartment might still be appropriate to be made available or subject to compartment restrictions even though they are not formally part of the compartment (see below about access rules).

5.7.2 Boundaries and Relationships

Compartment definitions describe how particular compartment instances are named and identified, and how systems know which resources are in the compartment. The following compartments are defined by this specification:

Title Description Identity Membership
Patient The set of resources associated with a particular patient There is an instance of the patient compartment for each patient resource, and the identity of the compartment is the same as the patient. When a patient is linked to another patient resource, the records associated with the linked patient resource will not be returned as part of the compartment search. Those records will be returned only with another compartment search using the "id" for the linked patient resource. In cases where two patients have been merged rather than linked, associated resources should be moved to the target patient as part of the merge process, so the patient compartment for the target patient would include all relevant data, and the patient compartment for the source patient would include only the linked Patient and possibly remnant resources like AuditEvent. The patient compartment includes any resources where the subject of the resource is the patient, and some other resources that are directly linked to resources in the patient compartment
Encounter The set of resources associated with a particular encounter There is an instance of the encounter compartment for each encounter resource, and the identity of the compartment is the same as the encounter The encounter compartment includes any resources where the resource has an explicitly nominated encounter, and some other resources that themselves link to resources in the encounter compartment. Note that for many resources, the exact nature of the link to encounter can be ambiguous (e.g. for a DiagnosticReport, is it the encounter when it was initiated, or when it was reported?)
RelatedPerson The set of resources associated with a particular 'related person' There is an instance of the relatedPerson compartment for each relatedPerson resource, and the identity of the compartment is the same as the relatedPerson The relatedPerson compartment includes any resources where the resource is explicitly linked to relatedPerson (usually as author)
Practitioner The set of resources associated with a particular practitioner There is an instance of the practitioner compartment for each Practitioner resource, and the identity of the compartment is the same as the Practitioner The practitioner compartment includes any resources where the resource is explicitly linked to a Practitioner (usually as author, but other kinds of linkage exist)
Device The set of resources associated with a particular device There is an instance of the device compartment for each Device resource, and the identity of the compartment is the same as the Device The device compartment includes any resources where the resource is explicitly linked to a Device (mostly subject or performer)
Group The set of resources associated with a particular group There is an instance of the group compartment for each Group resource, and the identity of the compartment is the same as the Group The device compartment includes any resources where the resource is explicitly linked to a Device (mostly subject or performer)

The full definitions of these compartments are published as CompartmentDefinition resources. Servers typically do not support the full definition of a compartment, and are not required to. Systems may publish CompartmentDefinition resources so that other systems may make use of compartments properly.

  • CompartmentDefinitions are used by CapabilityStatement instances for specifying how resources are accessed
  • GraphDefinition also provides a mechanism for grouping resources, though it does not provide an additional search mechanism. Inclusion of resources in a GraphDefinition supports more complex criteria for inclusion than that allowed by CompartmentDefinition.

5.7.3 References to this Resource

5.7.4 Resource Content

Structure

NameFlagsCard.TypeDescription & Constraintsdoco
.. CompartmentDefinition TU DomainResource Compartment Definition for a resource
+ Warning: Name should be usable as an identifier for the module by machine processing applications such as code generation

Elements defined in Ancestors: id, meta, implicitRules, language, text, contained, extension, modifierExtension
Interfaces Implemented: CanonicalResource
... url ΣC 1..1 uri Canonical identifier for this compartment definition, represented as a URI (globally unique)
+ Warning: URL should not contain | or # - these characters make processing canonical references problematic
... version Σ 0..1 string Business version of the compartment definition
... versionAlgorithm[x] Σ 0..1 How to compare versions
Binding: Version Algorithm (Extensible)
.... versionAlgorithmString string
.... versionAlgorithmCoding Coding
... title ΣT 0..1 string Name for this compartment definition (human friendly)
... status ?!Σ 1..1 code draft | active | retired | unknown
Binding: PublicationStatus (Required)
... experimental Σ 0..1 boolean For testing only - never for real usage
... date Σ 0..1 dateTime Date last changed
... publisher ΣT 0..1 string Name of the publisher/steward (organization or individual)
... contact Σ 0..* ContactDetail Contact details for the publisher

... description T 0..1 markdown Natural language description of the compartment definition
... useContext Σ 0..* UsageContext The context that the content is intended to support

... purpose T 0..1 markdown Why this compartment definition is defined
... code Σ 1..1 code Patient | Encounter | RelatedPerson | Practitioner | Device | EpisodeOfCare
Binding: Compartment Type (Required)
... search Σ 1..1 boolean Whether the search syntax is supported
... resource Σ 0..* BackboneElement How a resource is related to the compartment

.... code Σ 1..1 code Name of resource type
Binding: Resource Types (Required)
.... param Σ 0..* string Search Parameter Name, or chained parameters

.... documentation 0..1 string Additional documentation about the resource and compartment
.... startParam 0..1 uri Search Param for interpreting $everything.start
.... endParam 0..1 uri Search Param for interpreting $everything.end

doco Documentation for this format icon

See the Extensions for this resource

 

Additional definitions: Master Definition XML + JSON, XML Schema/Schematron + JSON Schema, ShEx (for Turtle) , the spreadsheet version & the dependency analysis

5.7.4.1 Terminology Bindings

Path ValueSet Type Documentation
CompartmentDefinition.versionAlgorithm[x] VersionAlgorithm Extensible

Indicates the mechanism used to compare versions to determine which is more current.
CompartmentDefinition.status PublicationStatus Required

The lifecycle status of an artifact.
CompartmentDefinition.code CompartmentType Required

Which type a compartment definition describes.
CompartmentDefinition.resource.code ResourceType Required

Concrete FHIR Resource Types

5.7.4.2 Constraints

UniqueKeyLevelLocationDescriptionExpression
img cnl-0Warning (base)Name should be usable as an identifier for the module by machine processing applications such as code generationname.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
img cnl-1Warning CompartmentDefinition.urlURL should not contain | or # - these characters make processing canonical references problematicexists() implies matches('^[^|# ]+$')

5.7.4.3 Base Resource

A compartment implicitly always includes the resource that is a 'root' of the compartment e.g. the resource Patient/123 is the root resource of the Patient Compartment for Patient/123. Thus an operation that retrieves everything within the compartment will include the base resource; a scope that grants access to everything within the compartment will grant access to the resource; etc.

5.7.4.4 Using Compartments

As an example of compartment usage, to retrieve a list of a patient's conditions, use the URL: 

  GET [base]/Patient/[id]/Condition

Additional search parameters can be defined, such as this hypothetical search for acute conditions: 

  GET [base]/Patient/[id]/Condition?code:in=http://hspc.org/ValueSet/acute-concerns

Note that as searches, these are syntactic variations on these two search URLs respectively: 

  GET [base]/Condition?patient=[id]
  GET [base]/Condition?patient=[id]&code:in=http://hspc.org/ValueSet/acute-concerns

The outcome of a compartment search is the same as the equivalent normal search. For example, both these searches return the same outcome if there is no patient 333: 

  GET [base]/Patient/333/Condition
  GET [base]/Condition?patient=333

Whether the patient doesn't exist, or the user has no access to the patient, both these searches return an empty bundle with no matches. Some systems will include an operation outcome warning that there is no matching patient.

However, there is a key difference in functionality between compartment based searches and direct searches with parameters. Consider this search: 

  GET [base]/Patient/[id]/Communication

Because the definition of the patient compartment for Communication says that a Communication resource is in the patient compartment if the subject, sender, or recipient is the patient, the compartment search is actually the same as the union of these 3 searches: 

  GET [base]/Communication?subject=[id]
  GET [base]/Communication?sender=[id]
  GET [base]/Communication?recipient=[id]

There is no way to do this as a single search, except by using the _filter: 

  GET [base]/Communication?_filter=subject re [id] or sender re [id] or recipient re [id]

Further details of searching by compartment are described under the search operation. As a search related operation, the assignment of resources to compartments is only based on the current version of any of the resources involved. Note that contained patient resources cannot create a patient compartment of their own.

Note that while this specification describes how to use the compartment syntax to find resources that are logically associated with the compartment, the compartment is not part of the identity of the resource. E.g. the response to the following is not defined by this specification: 

  GET [base]/Patient/[patient-id]/Condition/[resource-id]

The response for write operations (PUT/DELETE/PATCH) are also not defined by this specification. Nor is the response to a POST defined: 

  POST [base]/Patient/[patient-id]/Condition

There is no expectation for servers to support either read or write to such URLs.

5.7.4.5 Logical Meaning of Compartments

Compartments may be used explicitly, like this, but can also be used implicitly. For instance, if a FHIR server is providing a patient view of a record, the authorized user associated with use of the FHIR RESTful API may be limited to accessing records from the compartment instance(s) logically associated with their identity. Irrespective of whether compartments are being used explicitly or implicitly, servers will need to make arrangements to make some resources with no direct link to a patient available to the client (medications, substances, binaries, etc.).

Note that resources may cross between compartments, or interlink them. Examples of this would be where a Diagnostic Report identifies a subject, but an Observation it references identifies a different subject, or where a List resource references items that identify different subjects. Such cross-linking may arise for many valid reasons, including:

  • Cases where subject records are inter-linked - Transplants, Perinatal care, family therapy etc.
  • Workflow management where action lists link multiple patients and/or practitioners

Given the wide variety of use cases and contexts in which FHIR is used, compartments do not define how cross-linking is handled. Systems may reject resources, remove them from both compartments, or place them in both, or act in some other fashion.

The graph definition resource provides a method by which rules about cross-linking may be made and enforced.

It is at the discretion of the server whether to include resources in a compartment when the reference to the resource that establishes the compartment is in an extension.

Some resources are not in any compartment, e.g. Medication, Substance, Location. These resources are not linked directly to a patient or authored record, and are sometimes called 'master files'. Servers will need to make arrangements to make these resources available to the clients that are limited to particular compartments. For example, a Medication resource describes a medication itself and does not link to a patient; however, a resource such as MedicationAdministration connects the Medication (details of what was administered) to the patient (for whom was it administered), and so is required to interpret the administration.

5.7.5 Defining New Compartments

Compartments are defined and added to the list above when implementer communities identify them as common access points for data. As described below, compartments have both syntactical and logical consequences, and both these aspects of their functionality are evaluated when deciding whether to define compartments.

5.7.6 Search Parameters

Search parameters for this resource. See also the full list of search parameters for this resource, and check the Extensions registry for search parameters on extensions related to this resource. The common parameters also apply. See Searching for more information about searching in REST, messaging, and services.

Name Type Description Expression In Common
code token Patient | Encounter | RelatedPerson | Practitioner | Device CompartmentDefinition.code
context token A use context assigned to the compartment definition (CompartmentDefinition.useContext.value.ofType(CodeableConcept)) 30 Resources
context-quantity quantity A quantity- or range-valued use context assigned to the compartment definition (CompartmentDefinition.useContext.value.ofType(Quantity)) | (CompartmentDefinition.useContext.value.ofType(Range)) 30 Resources
context-type token A type of use context assigned to the compartment definition CompartmentDefinition.useContext.code 30 Resources
context-type-quantity composite A use context type and quantity- or range-based value assigned to the compartment definition On CompartmentDefinition.useContext:
  context-type: code
  context-quantity: value.ofType(Quantity) | value.ofType(Range)		 30 Resources
context-type-value composite A use context type and value assigned to the compartment definition On CompartmentDefinition.useContext:
  context-type: code
  context: value.ofType(CodeableConcept)		 30 Resources
date date The compartment definition publication date CompartmentDefinition.date 31 Resources
description string The description of the compartment definition CompartmentDefinition.description 29 Resources
name string Computationally friendly name of the compartment definition CompartmentDefinition.name 28 Resources
publisher string Name of the publisher of the compartment definition CompartmentDefinition.publisher 31 Resources
resource token Name of resource type CompartmentDefinition.resource.code
status token The current status of the compartment definition CompartmentDefinition.status 35 Resources
url uri The uri that identifies the compartment definition CompartmentDefinition.url 34 Resources
version token The business version of the compartment definition CompartmentDefinition.version 32 Resources