Defines the characteristics of a message that can be shared between systems, including the type of event that initiates the message, the content to be transmitted and what response(s), if any, are permitted.

Allows messages to be defined once and re-used across systems.

This would be a MIF-level artifact.

The business identifier that is used to reference the MessageDefinition and is expected to be consistent from server to server.

Allows the message definition to be referenced by a single globally unique identifier.

Can be a urn:uuid: or a urn:oid: but real http: addresses are preferred. Multiple instances may share the same URL if they have a distinct version.

The determination of when to create a new version of a resource (same url, new version) vs. defining a new artifact is up to the author. Considerations for making this decision are found in Technical and Business Versions.

In some cases, the resource can no longer be found at the stated url, but the url itself cannot change. Implementations can use the meta.source element to indicate where the current master source of the resource can be found.

A formal identifier that is used to identify this message definition when it is represented in other formats, or referenced in a specification, model, design or an instance.

Allows externally provided and/or usable business identifiers to be easily associated with the module.

Typically, this is used for identifiers that can go in an HL7 V3 II (instance identifier) data type, and can then identify this message definition outside of FHIR, where it is not possible to use the logical URI.

The identifier that is used to identify this version of the message definition when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the message definition author and is not expected to be globally unique. For example, it might be a timestamp (e.g. yyyymmdd) if a managed version is not available. There is also no expectation that versions can be placed in a lexicographical sequence.

There may be different message definition instances that have the same identifier but different versions. The version can be appended to the url in a reference to allow a reference to a particular business version of the message definition with the format [url]|[version]. The version SHOULD NOT contain a '#' - see Business Version.

Indicates the mechanism used to compare versions to determine which is more current.

If set as a string, this is a FHIRPath expression that has two additional context variables passed in - %version1 and %version2 and will return a negative number if version1 is newer, a positive number if version2 and a 0 if the version ordering can't be successfully be determined.

A natural language name identifying the message definition. This name should be usable as an identifier for the module by machine processing applications such as code generation.

Support human navigation and code generation.

The name is not expected to be globally unique. The name should be a simple alphanumeric type name to ensure that it is machine-processing friendly.

A short, descriptive, user-friendly title for the message definition.

This name does not need to be machine-processing friendly and may contain punctuation, white-space, etc.

A MessageDefinition that is superseded by this definition.

The status of this message definition. Enables tracking the life-cycle of the content.

Allows filtering of message definitions that are appropriate for use versus not.

A Boolean value to indicate that this message definition is authored for testing purposes (or education/evaluation/marketing) and is not intended to be used for genuine usage.

Enables experimental content to be developed following the same lifecycle that would be used for a production-level message definition.

Allows filtering of message definitions that are appropriate for use versus not.

The date (and optionally time) when the message definition was last significantly changed. The date must change when the business version changes and it must change if the status code changes. In addition, it should change when the substantive content of the message definition changes.

The date is often not tracked until the resource is published, but may be present on draft content. Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the message definition. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource.

The name of the organization or individual responsible for the release and ongoing maintenance of the message definition.

Helps establish the "authority/credibility" of the message definition. May also allow for contact.

Usually an organization but may be an individual. The publisher (or steward) of the message definition is the organization or individual primarily responsible for the maintenance and upkeep of the message definition. This is not necessarily the same individual or organization that developed and initially authored the content. The publisher is the primary point of contact for questions or issues with the message definition. This item SHOULD be populated unless the information is available from context.

Contact details to assist a user in finding and communicating with the publisher.

May be a web site, an email address, a telephone number, etc.

A free text natural language description of the message definition from a consumer's perspective.

This description can be used to capture details such as comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the message definition as conveyed in the 'text' field of the resource itself. This item SHOULD be populated unless the information is available from context (e.g. the language of the message definition is presumed to be the predominant language in the place the message definition was created).

The content was developed with a focus and intent of supporting the contexts that are listed. These contexts may be general categories (gender, age, ...) or may be references to specific programs (insurance plans, studies, ...) and may be used to assist with indexing and searching for appropriate message definition instances.

Assist in searching for appropriate content.

When multiple useContexts are specified, there is no expectation that all or any of the contexts apply.

A legal or geographic region in which the message definition is intended to be used.

It may be possible for the message definition to be used in jurisdictions other than those for which it was originally designed or intended.

Explanation of why this message definition is needed and why it has been designed as it has.

This element does not describe the usage of the message definition. Instead, it provides traceability of ''why'' the resource is either needed or ''why'' it is defined as it is. This may be used to point to source materials or specifications that drove the structure of this message definition.

A copyright statement relating to the message definition and/or its contents. Copyright statements are generally legal restrictions on the use and publishing of the message definition.

Consumers must be able to determine any legal restrictions on the use of the message definition and/or its content.

A short string (<50 characters), suitable for inclusion in a page footer that identifies the copyright holder, effective period, and optionally whether rights are resctricted. (e.g. 'All rights reserved', 'Some rights reserved').

Defines the content expected to be rendered in all representations of the artifact.

The (c) symbol should NOT be included in this string. It will be added by software when rendering the notation. Full details about licensing, restrictions, warrantees, etc. goes in the more general 'copyright' element.

The MessageDefinition that is the basis for the contents of this resource.

Identifies a protocol or workflow that this MessageDefinition represents a step in.

It should be possible to use MessageDefinition to describe a message to be used by certain steps in a particular protocol as part of a PlanDefinition or ActivityDefinition.

Event code or link to the EventDefinition.

The impact of the content of the message.

Identifies the resource (or resources) that are being addressed by the event. For example, the Encounter for an admit message or two Account records for a merge.

The kind of resource that must be the focus for this message.

Multiple focuses addressing different resources may occasionally occur. E.g. to link or unlink a resource from a particular account or encounter, etc.

A profile that reflects constraints for the focal resource (and potentially for related resources).

This profile allows setting boundaries for what content must appear within the message bundle vs. outside based on the declared aggregation constraints on referenced resources on this and related profiles.

This should be present for most message definitions. However, if the message focus is only a single resource and there is no need to include referenced resources or otherwise enforce the presence of particular elements, it can be omitted.

Identifies the minimum number of resources of this type that must be pointed to by a message in order for it to be valid against this MessageDefinition.

Identifies the maximum number of resources of this type that must be pointed to by a message in order for it to be valid against this MessageDefinition.

Declare at a message definition level whether a response is required or only upon error or success, or never.

This enables the capability currently available through MSH-16 (Application Level acknowledgement) in HL7 Version 2 to declare at a message instance level whether a response is required or only upon error or success, or never.

Indicates what types of messages may be sent as an application-level response to this message.

This indicates an application level response to "close" a transaction implicit in a particular request message. To define a complete workflow scenario, look to the [[PlanDefinition]] resource which allows the definition of complex orchestrations, conditionality, etc.

A reference to the message definition that must be adhered to by this supported response.

Provides a description of the circumstances in which this response should be used (as opposed to one of the alternative responses).

Graph is Canonical reference to a GraphDefinition. If a URL is provided, it is the canonical reference to a GraphDefinition that it controls what additional resources are to be added to the Bundle when building the message. The GraphDefinition can also specify profiles that apply to the various resources.