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2:3.96 Query Code System [ITI-96]

This section corresponds to transaction [ITI-96] of the IHE IT Infrastructure Technical Framework. Transaction [ITI-96] is used by the Terminology Consumer and Terminology Repository Actors.

2:3.96.1 Scope

This transaction is used by the Terminology Consumer to solicit information about code systems whose data match data provided in the query parameters on the request message. The request is received by the Terminology Repository. The Terminology Repository processes the request and returns a response of the matching code systems.

2:3.96.2 Actor Roles

Table 2:3.96.2-1: Actor Roles

2:3.96.3 Referenced Standards

• HL7 FHIR standard R4 http://hl7.org/fhir/R4/index.html

2:3.96.4 Messages

Figure 2:3.96.4-1: Interaction Diagram

2:3.96.4.1 Search Code System Request Message

The Search Code System message is a FHIR search interaction on the CodeSystem Resource.

2:3.96.4.1.1 Trigger Events

A Terminology Consumer triggers a Search Code System Request to a Terminology Repository according to the business rules for the search. These business rules are outside the scope of this transaction.

2:3.96.4.1.2 Message Semantics

A Terminology Consumer initiates a search interaction using HTTP GET as defined at http://hl7.org/fhir/R4/http.html#search on the CodeSystem. The query parameters are identified below. A Terminology Consumer may query any combination or subset of the parameters. The target is formatted as:

GET [base]/CodeSystem?[parameter=value]

Where [base] is the URL of Terminology Repository.

A Terminology Repository shall support responding to a request for both the JSON and the XML messaging formats as defined in FHIR. A Terminology Consumer shall accept either the JSON or the XML messaging formats as defined in FHIR. See ITI TF-2: Appendix Z.6 for more details.

A Terminology Repository shall implement the parameters described below. A Terminology Repository may choose to support additional query parameters beyond the subset listed below. Any additional query parameters supported shall be supported according to the core FHIR specification.

See ITI TF-2: Appendix W for informative implementation material for this transaction.

2:3.96.4.1.2.1 Query Parameters

The Terminology Repository shall support the :contains and :exact modifiers in all of the string query parameters below defined at http://hl7.org/fhir/R4/search.html#string.

The Terminology Repository shall support the following search parameters as defined at http://hl7.org/fhir/R4/search.html#all and http://hl7.org/fhir/R4/codesystem.html#search.

_id
_lastUpdated
status
identifier
name
description
system
title
url
version

The Terminology Repository shall also support the following prefixes for the _lastUpdated parameter: gt, lt, ge, le, sa, and eb.

2:3.96.4.1.3 Expected Actions

The Terminology Repository shall process the query to discover the code systems that match the search parameters given, and return a response as per Section 2:3.96.4.2 or an error as per http://hl7.org/fhir/R4/search.html#errors.

2:3.96.4.2 Search Code System Response Message

2:3.96.4.2.1 Trigger Events

The Terminology Repository found code systems matching the query parameters specified by the Terminology Consumer as a result of a Search Code System Request.

2:3.96.4.2.2 Message Semantics

The Terminology Repository shall support the search response message as defined at http://hl7.org/fhir/R4/http.html#search on the CodeSystem, as defined at http://hl7.org/fhir/R4/codesystem.html.

The “content-type” of the response will depend upon the requested response format indicated by the Terminology Consumer.

See ITI TF-2: Appendix Z.6 for more details on response format handling. See ITI TF-2: Appendix Z.7 for handling guidance for Access Denied.

2:3.96.4.2.2.1 FHIR CodeSystem Resource Constraints

A CodeSystem Resource returned by the Terminology Repository shall be further constrained as described in the CodeSystem Profile for SVCM.

2:3.96.4.2.3 Expected Actions

The Terminology Consumer has received the response and continues with its workflow.

2:3.96.4.3 Read Code System Request Message

This message represents an HTTP GET from the Terminology Consumer to the Terminology Repository and provides a mechanism for retrieving a single CodeSystem with a known resource id.

2:3.96.4.3.1 Trigger Events

When the Terminology Consumer possesses the id of the CodeSystem (either through query, database lookup, or other mechanism) for which it requires additional or new information, it issues a Read Code System Request.

2:3.96.4.3.2 Message Semantics

A Terminology Consumer initiates a read interaction using HTTP GET as defined at http://hl7.org/fhir/R4/http.html#read on the CodeSystem Resource. The target is formatted as:

GET [base]/CodeSystem/[resourceId]

Where [base] is the URL of Terminology Repository.

The resourceId included in the request always represents the unique id for the CodeSystem within the scope of the URL. For example, while http://example1.org/ihe/CodeSystem/1 and http://example2.com/ihe/CodeSystem/1 both contain the same [resourceId], they reference two different resource instances.

Note: The use of “http” or “https” in URL does not override requirements to use TLS for security purposes.

A Terminology Repository shall support responding to a request for both the JSON and the XML messaging formats as defined in FHIR. A Terminology Consumer shall accept either the JSON or the XML messaging formats as defined in FHIR. See ITI TF-2: Appendix Z.6 for more details.

See ITI TF-2: Appendix W for informative implementation material for this transaction.

2:3.96.4.3.3 Expected Actions

The Terminology Repository shall process the request to retrieve the CodeSystem that matches the given resource id, and return a response as defined at http://hl7.org/fhir/R4/http.html#read or an error code as defined at http://hl7.org/fhir/http.html#Status-Codes.

2:3.96.4.4 Read Code System Response Message

The Terminology Repository’s response to a successful Read Code System message shall be an HTTP 200 (OK) Status code with a CodeSystem Resource, or an appropriate error status code, optionally with an OperationOutcome Resource.

2:3.96.4.4.1 Trigger Events

The Terminology Repository found a CodeSystem Resource matching the resource identifier specified by the Terminology Consumer.

2:3.96.4.4.2 Message Semantics

The Read Code System Response is sent from the Terminology Repository to the Terminology Consumer as a single CodeSystem, as defined at http://hl7.org/fhir/R4/codesystem.html and constrained by the CodeSystem Profile for SVCM.

The “content-type” of the response will depend upon the requested response format indicated by the Terminology Consumer.

See ITI TF-2: Appendix Z.6 for more details on response format handling. See ITI TF-2: Appendix Z.7 for handling guidance for Access Denied.

If the Terminology Repository is unable to produce a response in the requested format, it shall respond with an HTTP 4xx error indicating that it was unable to fulfill the request. The Terminology Repository may be capable of servicing requests for response formats not listed, but shall, at minimum, be capable of producing XML and JSON encodings.

2:3.96.4.4.3 Expected Actions

The Terminology Consumer has received the response and continues with its workflow.

2:3.96.5 Security Considerations

See the general Security Consideration in ITI TF-1: 51.5.

2:3.96.5.1 Security Audit Considerations

Note that the same audit message is recorded by both Terminology Consumer and Repository. The difference being the Audit Source element. Both sides record to show consistency between the message sent by the Consumer and the action taken at the Registry.

The actors involved shall record audit events according to the Audit Event for Query Code System for Read by the Terminology Consumer and Repository or the Audit Event for Query Code System for Query by the Terminology Consumer and Repository.