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6.3 Resource Other - Content

Other is a conformant for handling resource concepts not yet defined for FHIR or outside HL7's scope of interest.

6.3.3 Resource Content

<Other xmlns="http://hl7.org/fhir"> 
 <!-- from Resource: extension, modifierExtension, language, text, and contained -->
 <identifier><!-- 0..* Identifier Business identifier --></identifier>
 <code><!-- 1..1 CodeableConcept Kind of Resource --></code>
 <subject><!-- 0..1 Resource(Any) Identifies the --></subject>
 <author><!-- 0..1 Resource(Practitioner|Patient|RelatedPerson) Who created --></author>
 <created value="[date]"/><!-- 0..1 When created -->
</Other>

Alternate definitions: Schema/Schematron, Resource Profile

6.3.3.1 Terminology Bindings

6.3.4 Why not custom resources?

Technically, nothing prevents implementers from going off and defining their own resources containing whatever data elements they wish. However, doing so causes several issues:

• Custom resources don't have a discoverability mechanism in the same way custom codes and extensions do using the ValueSet and Profile resources. As a result, any implementer that receives a custom resource would have no way of looking up what the meaning of the resource or its elements were. While they could get some sense of meaning from XML or JSON tag names, this often isn't sufficient for safe healthcare interoperability.
• Custom resource names would not be present in the FHIR schemas as allowed elements within the FHIR ATOM schema and would also not be present in the enumeration of resources in the ResourceReference type. This would cause issues for any receiving system making use of the schemas directly or via code-generation.
• There is no means of ensuring that two implementers might independently come up with the same name for a resource but define it differently in terms of meaning as well as allowed elements. This would also cause interoperability issues.

All of these concerns are mitigated when there's an assumption that the custom resource will only be used within a narrow constrained environment where all participants will be aware of the semantics, will be using the same custom schemas and there's no chance of collisions. However, HL7's experience is that closed implementation environments rarely remain that way over the long term. Eventually data will need to be shared with others outside the closed environment and all of the above issues will again come into play.

Therefore, use of 'custom' resources is NOT considered to be conformant with FHIR. While the use of extensions may make the Other resource slightly more complex and less visually appealing, it is the only safe and approved mechanism for sharing resource concepts not representable using standard HL7-defined resources.

NOTE: This position is subject to change based on implementation experience. Alternative mechanisms for handling custom resource requirements in a safe manner may be explored. Ideas around alternative technical strategies for managing this issue are welcome.

6.3.5 Best practices for using 'Other'

There are several good practices to follow when making use of the Other resource:

1. Before using Other, post a description of the desired resource type on HL7's FHIR list-server or on Stack Overflow to see whether the use-case can be met by an existing resource. (Sometimes the intended scope of an existing resource won't be clear, even if the intent is to cover your space.) Using an existing resource is usually preferable to using Other as it significantly increases the likelihood of interoperability.
2. If an existing resource would normally be a good fit for your use-case but can't be used due to overly prescriptive constraints your implementation is unable to meet, again raise the problem on Stack Overflow so the problem with the specification can be addressed
3. If it is necessary to make use of the Other resource, try to use one of the HL7-defined codes for resource type or submit your requirement for a new type for inclusion in the HL7 vocabulary, as this will increase the likelihood of interoperability. Alternate code systems are conformant, but are less likely to be recognized or re-used across the healthcare implementation space.
4. Architect your interface in a way that will make it less painful to swap your use of Other with an 'official' resource in the event that a future release of FHIR formally defines a resource that encompasses your use-case.
5. Use a Profile to define the extensions relevant to each type of other resource used. Profile can also be used to define additional search criteria appropriate for the resource.

Other should always be defined by the use of a

6.3.6 Referencing Other resources

None of the standard resources will have direct references to Other, aside from those that allow linking to "Any" resource. As a result, most references to "Other" will need to be performed using extensions.

6.3.7 Search Parameters

Search parameters for this resource. The standard parameters also apply. See Searching for more information about searching in REST, messaging, and services.