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2.4 Resource Bundle - Content

FHIR Infrastructure Work Group

Maturity Level: N

Normative (from v4.0.0)

Security Category: Not Classified

Compartments: Not linked to any defined compartments

A container for a collection of resources.

2.4.3 References to this Resource

No references for this Resource.

2.4.4 Resource Content

 

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

2.4.4.1 Terminology Bindings

Path	Definition	Type	Reference
Bundle.type	Indicates the purpose of a bundle - how it is intended to be used.	Required	BundleType
Bundle.link.relation	Link Relation Types defined at https://www.iana.org/assignments/link-relations/link-relations.xhtml#link-relations-1	Required	LinkRelationTypes
Bundle.entry.search.mode	Why an entry is in the result set - whether it's included as a match or because of an _include requirement, or to convey information or warning information about the search process.	Required	SearchEntryMode
Bundle.entry.request.method	HTTP verbs (in the HTTP command line). See HTTP rfc for details.	Required	HTTPVerb

2.4.4.2 Constraints

2.4.4.3 Notes about Bundle

• Conceptually, a bundle is a list of resources with some context (named links, and status on the entries)
• Since a Bundle is itself a Resource it has the same common metadata as all resources, including profile assertions, tags, and security labels. Note that the values in Bundle.meta.security will generally be influenced by the meta.security values of the entries within the Bundle; see http://hl7.org/fhir/security.html
• Although there are no extensions on the Bundle itself, link, entry, and search/request/response can all have extensions. See Patient and Location for examples on search
• Both Bundle.link and Bundle.entry.link are defined to support providing additional context when Bundles are used (e.g. HATEOAS ). Bundle.entry.link corresponds to links found in the HTTP header if the resource in the entry was read directly. This specification defines some specific uses of Bundle.link for searching and paging, but no specific uses for Bundle.entry.link, and no defined function in a transaction - meaning is implementation specific
• Bundles have both .id and .identifier - see Resource Identities for further information

2.4.4.4 Using Bundles

The content and rules for using a Bundle depend on the type of the bundle. Note that all bundle types use resource identity resolution as described below.

2.4.4.4.1 Document

A document Bundle (type = "document") consists of a series of entries, the first of which is a Composition. Each entry element SHALL contain a resource. See Documents for further information.

Example

2.4.4.4.2 Message

A message Bundle (type = "message") consists of a series of entries, the first of which is a MessageHeader. Each entry element SHALL contain a resource. See Messaging for further information.

Example Request and Response

2.4.4.4.3 Search Results

A set of search results (type = "searchset") consists of a series of 0 or more entries. Each entry element SHALL contain a resource. See Search for further information.

In addition, Bundle.total may be used to return the total number of resources that match the search, and that may be returned by following the "next" link. This total MAY be an estimate. Full iteration of the search set or using _total=accurate are the only mechanisms to reliably determine an exact count against an arbitrary system.

For each entry, a search set can also contain two specific pieces of search related information:

• search.mode: An indication of whether the resource is in the search set because it matched the search criteria or whether it is included because another resource refers to it (e.g. by the _include parameter)
• search.score: The server's search ranking score for the entry. Servers are not required to return a ranking score, but if they do, 1 is most relevant, and 0 is least relevant. Note: often, search results are sorted by score, but the client may specify a different sort order (see Search Relevance)

Example

2.4.4.4.4 History

A change history (type = "history") consists of a series of 0 or more entries. Each entry element SHALL contain a request element that describes the change that was made and, if the method is a POST, PATCH, or PUT, a resource that represents the state of the resource at the conclusion of the operation. A response element SHALL also be present so that consumers can access the location header. See History for further information.

In addition, Bundle.total may be used to return the total number of resources that are included in the change history, including those that may be returned by following the "next" link.

2.4.4.4.5 Transaction / Batch

A transaction (type = "transaction") or batch (type = "batch") consists of a series of 0 or more entries. Each entry element SHALL contain a request element has the details of an HTTP operation that informs the system processing the transaction what to do with the entry. If the entry method is a 'PUT' or 'POST', then the entry SHALL contain a resource that becomes the body of the HTTP operation. See Transactions for further information.

Example

2.4.4.4.6 Transaction/Batch Response

A transaction response (type = "transaction-response") or batch response (type="batch-response") consists of a series of 0 or more entries: 1 for each entry in the transaction or batch it is in response to. Each entry element SHALL contain a response element which indicates the outcome of the HTTP operation that the server performed for the entry.

Example

2.4.4.4.7 Collection

A collection (type = "collection") consists of a series of 0 or more entries. No particular use with respect to the FHIR specification is associated with this Bundle. Each entry element SHALL contain a resource.

Example

2.4.4.4.8 Subscription Notification

Normative Candidate Note: This BundleType is not normative - it is still undergoing Trial Use while more experience is gathered.

A subscription notification (type = "subscription-notification") consists of a series of 1 or more entries, the first of which is a SubscriptionStatus. There may be additional contents, as specified by the subscription responsible for generating the notification. See Subscription for further information.

Examples

2.4.5 Resource URL & Uniqueness rules in a bundle

Except for transactions and batches, each entry in a Bundle SHALL have a fullUrl which is the identity of the resource in the entry. Note that this is not a versioned reference to the resource, but its identity. Where a resource is not assigned a persistent identity that can be used in the Bundle, a UUID SHALL be used in fullUrl (urn:uuid:...).

For transactions and batches, entries MAY omit fullURLs when the entry.request.method = POST, and the resource has no identity. Note that even in this case, there may still be a fullURL in a transaction when entry.request.method = POST so that relationships between resources can be represented (see Transactions).

A given version of a resource SHALL only appear once in each Bundle. There MAY, however, be multiple versions of a single resource present in a single bundle. This would be expected in Bundles of type history, and also might be necessitated by closely tracking Provenance.

Note that the meaning of an unversioned reference to a resource that appears multiple times is potentially ambiguous, though processors may have additional information to help resolve this (e.g. change order in a history bundle).

When processing batches and transactions, it is at server discretion how to behave if multiple versions of a single resource are present.

2.4.5.1 Resolving references in Bundles

The Bundle resource is a packaging construct that has one of more entries that are other kinds of resources. Those resources themselves have references to other resources - e.g. an Observation that refers to a Patient. The referenced resources may also be found in the Bundle. For example, the system that constructed the Bundle may have included both the Observation and the Patient. The content of the references between resources doesn't change because of the bundle.

This section documents a method that resolves references correctly within a bundle. Note that this method does not define any new semantics; resolution is based on the way resource identity and resource references work.

Applications reading a Bundle should always look for a resource by its identity in the bundle first before trying to access it by its URL externally.

Note that reference.value in entry resources can use any URI scheme (in addition to using relative values like "Patient/123").

How to resolve a reference in a Bundle:

Resolving urns. If the reference.value is a URN (always absolute) (e.g. "urn:uuid:9d1714da-b7e6-455b-bfd2-69ce0ff5fb12")

• Look for an entry with a fullUrl that matches the reference.value
• If one is found, the resolution succeeds (and ends) here
• Otherwise, the resolution fails (and ends) here. The reference has no defined meaning within this specification.

Resolving absolute references. If the reference.value is an absolute URL (e.g., "https://fhir.example.org/base/Patient/123", "https://fhir.example.org/base/Patient/123/_history/a"):

• If the reference.value is versionless (i.e. it has no "/_history/" path segment - e.g. "https://fhir.example.org/base/Patient/123"):
  • Look for an entry with a fullUrl that matches the reference.value
  • If one is found, the resolution succeeds (and ends) here
  • If more than one is found, the server MAY look for the most recent version (based on meta.lastUpdated). If it is able to find exactly one most recent this way, the resolution succeeds (and ends) here
• If the reference.value includes a "_history" path segment (e.g. "https://fhir.example.org/base/Patient/123/_history/a"), split the value into two parts: a versionless reference (e.g. "https://fhir.example.org/base/Patient/123" and a version id (e.g. "a")
  • Look for an entry with a fullUrl that matches the versionless reference and a resource.meta.versionId that matches the reference's version id.
  • If a single record is found, the resolution succeeds (and ends) here.
  • If multiple records are found, it is an error.
• Optionally, attempt to resolve the URI if possible (e.g. by issuing a FHIR [read] on an https URL if not version-specific or a [vread] it the URL is version-specific).
  • If found, the resolution succeeds (and ends) here.
  • Otherwise, the resolution fails (and ends) here. The reference has no defined meaning within this specification.

Resolving relative references against a RESTful base. If the reference.value is of the form "[type]/[id]" (e.g., "Patient/123"):

• If the Bundle entry containing the reference has a fullUrl matching the RESTful URL regex (e.g., "https://fhir.example.org/Observation/456"):
  • Extract the [root] from the Bundle entry's fullUrl and append the relative reference to it (e.g., "https://fhir.example.org/" + "Patient/123" --> "https://fhir.example.org/Patient/123")
  • Follow the steps for Resolving absolute references above
• If the Bundle entry containing the reference does not have a fullUrl that matches the [RESTful URL regex] and the Bundle is a batch or transaction and the entry.request.method is POST, PUT or PATCH
  • take the base URL of the server that is the target of the batch/transaction and append the relative reference to it (e.g., transaction is being posted to "https://fhir.somewhere.org", then the expanded reference would be "https://fhir.somewhere.org/Patient/123"
  • Follow the steps for Resolving absolute references above

Resolving conditional references. If the reference occurs in a transaction Bundle and the reference.value is a conditional reference (e.g. "http://example.org/base/Patient?identifier=1234"):

• Perform the [search] specified in the conditional reference on the server.
  • If the search succeeds with a single resource, the resolution succeeds (and ends) here.
  • If the search succeeds with multiple matching resources, resolution fails (and ends) here. An error SHOULD be raised.
• Otherwise the resolution fails (and ends) here.

Resolving other references. If the rules above do not apply, the resolution fails (and ends) here. The reference has no defined meaning within this specification.

Note that the rules for resolving references in contained resources are the same as those for resolving references in the resource that contains the contained resource. I.e. the fullUrl of the containing resource is used when determining the base for relative references, etc.

Several portions of this algorithm are dependent on on the presence of Bundle.entry.fullUrl. In instances where references might be resolved within a Bundle but entries do not have fullURLs, resolution expectations are undefined. For this reason, Bundles where cross-Bundle references are present SHOULD always populate Bundle.entry.fullUrl.

If multiple matches are found (except where explicitly handled in the above algorithm), it is ambiguous which is correct. Applications MAY return an error or take some other action as they deem appropriate

There is an example Bundle that demonstrates these rules.

2.4.5.2 Serving Bundles using the RESTful API

The Bundle resource type has an end-point like all most other resources. This end-point serves the usual interactions. Bundles are treated as static resources on the /Bundle end-point (i.e. when a batch, transaction, or message is POSTed to /Bundle, it is stored as is, and the content is not processed as batch, transaction, or message - instead, they are processed like normal resource, with indexing / auditing etc. Performing a GET /[base]/Bundle/[location] will return the same resource.

The Bundle end point does have two special search parameters - composition and message, which allow for chained search into the first (special) entries in document and message resources.

All elements in Bundle are marked as summary because Bundle resources need to be fully populated when doing a search, and most use cases for retrieving summaries of documents or other types of bundles are not well suited by the standard isSummary mechanism and are better handles by operations or other mechanisms.

Note to Implementers: If an element marked as 'summary' is itself a nested resource (i.e. type is Resource), then the expectation is that the conveyed resource will also be expressed in its summary form. The typical place this applies is Bundle.entry.resource. This statement is left as STU because there is not yet significant implementer experience on its ramifications.

2.4.5.3 Signatures

The Bundle resource includes a signature element (digital signature) which can be used for standards based integrity verification and non-repudiation purposes. The Signature datatype provides details on use of the signature element. The Signature.type coded value of "Source" should be used when the signature is for simply proving that the resource content is the same as it was when the resource was updated or created.

2.4.6 Search Parameters

Search parameters for 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
composition	reference	The first resource in the bundle, if the bundle type is "document" - this is a composition, and this parameter provides access to search its contents	Bundle.entry[0].resource as Composition
identifier	token	Persistent identifier for the bundle	Bundle.identifier
message	reference	The first resource in the bundle, if the bundle type is "message" - this is a message header, and this parameter provides access to search its contents	Bundle.entry[0].resource as MessageHeader
timestamp	date	When the bundle was assembled	Bundle.timestamp
type	token	document | message | transaction | transaction-response | batch | batch-response | history | searchset | collection | subscription-notification	Bundle.type