A set of healthcare-related information that is assembled together into a single logical package that provides a single coherent statement of meaning, establishes its own context and that has clinical attestation with regard to who is making the statement. A Composition defines the structure and narrative content necessary for a document. However, a Composition alone does not constitute a document. Rather, the Composition must be the first entry in a Bundle where Bundle.type=document, and any other resources referenced from Composition must be included as subsequent entries in the Bundle (for example Patient, Practitioner, Encounter, etc.).

While the focus of this specification is on patient-specific clinical statements, this resource can also apply to other healthcare-related statements such as study protocol designs, healthcare invoices and other activities that are not necessarily patient-specific or clinical.

A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content. Often, this is a reference to an implementation guide that defines the special rules along with other profiles etc.

Asserting this rule set restricts the content to be only understood by a limited set of trading partners. This inherently limits the usefulness of the data in the long term. However, the existing health eco-system is highly fractured, and not yet ready to define, collect, and exchange data in a generally computable sense. Wherever possible, implementers and/or specification writers should avoid using this element. Often, when used, the URL is a reference to an implementation guide that defines these special rules as part of its narrative along with other profiles, value sets, etc.

The base language in which the resource is written.

Language is provided to support indexing and accessibility (typically, services such as text to speech use the language tag). The html language tag in the narrative applies to the narrative. The language tag on the resource may be used to specify the language of other presentations generated from the data in the resource. Not all the content has to be in the base language. The Resource.language should not be assumed to apply to the narrative automatically. If a language is specified, it should it also be specified on the div element in the html (see rules in HTML5 for information about the relationship between xml:lang and the html lang attribute).

IETF language tag for a human language

These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, nor can they have their own independent transaction scope. This is allowed to be a Parameters resource if and only if it is referenced by a resource that provides context/meaning.

This should never be done when the content can be identified properly, as once identification is lost, it is extremely difficult (and context dependent) to restore it again. Contained resources may have profiles and tags in their meta elements, but SHALL NOT have security labels. Contained resources may be a resource type defined in the FHIR specification, or an additional resource.

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.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

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

A free text natural language description of the artifact 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 artifact 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 artifact is presumed to be the predominant language in the place the artifact was created).

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

This element does not describe the usage of the artifact. 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 artifact.

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

The short copyright declaration (e.g. (c) '2015+ xyz organization' should be sent in the copyrightLabel element.

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 is expected to be added by software when rendering the notation. Full details about licensing, restrictions, warrantees, etc. goes in the more general 'copyright' element.

The date on which the guideline was approved by the publisher.

The date may be more recent than the approval date because of minor changes / editorial corrections.

The date on which the guideline was last updated.

If specified, this is usually after the approval date.

The period during which the guideline is intended to be in use.

The effective period for a resource determines when the content is applicable for usage and is independent of publication and review dates. For example, a measure intended to be used for the year 2016 would be published in 2015.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The end of the period. If the end of the period is missing, it means no end was known or planned at the time the instance was created. The start may be in the past, and the end date in the future, which means that period is expected/planned to end at that time.

The end value includes any matching date/time. i.e. 2012-02-03T10:00:00 is in a period that has an end value of 2012-02-03.

The Resource contains content in a language additional to the one in the language element.

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

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

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The purpose/type of contact.

If no purpose is defined, then these contact details may be used for any purpose.

The purpose for which an extended contact detail should be used.

The date on which the current version of the guideline was published.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The status of the processing for making the artifact publicly available, not necessarily the same as artifact status (Resource.status).

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

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

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The purpose/type of contact.

If no purpose is defined, then these contact details may be used for any purpose.

The purpose for which an extended contact detail should be used.

The name of an individual to contact, some types of contact detail are usually blank.

If there is no named individual, the telecom/address information is not generally monitored by a specific individual.

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

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

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The purpose/type of contact.

If no purpose is defined, then these contact details may be used for any purpose.

The purpose for which an extended contact detail should be used.

The name of an individual to contact, some types of contact detail are usually blank.

If there is no named individual, the telecom/address information is not generally monitored by a specific individual.

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

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

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The purpose/type of contact.

If no purpose is defined, then these contact details may be used for any purpose.

The purpose for which an extended contact detail should be used.

The name of an individual to contact, some types of contact detail are usually blank.

If there is no named individual, the telecom/address information is not generally monitored by a specific individual.

The date on which the guideline was first published in its initial version.

The date on which this version of the guideline was submitted for publication.

The period during which the guideline is open for consultation.

The date on which the guideline is planned to be completed.

The date when the guideline registration was submitted.

The date on which the composition content was last reviewed. Review happens periodically after that, but doesn't change the original approval date.

If specified, this is usually after the approval date.

The date on which the asset content was approved by the publisher. Approval happens once when the content is officially approved for usage.

The date may be more recent than the approval date because of minor changes / editorial corrections.

The period during which the composition content was or is planned to be effective.

The effective period for a composition determines when the content is applicable for usage and is independent of publication and review dates. For example, a measure intended to be used for the year 2016 would be published in 2015.

May be used to represent additional information that is not part of the basic definition of the resource and that modifies the understanding of the element that contains it and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

A version-independent identifier for the Composition. This identifier stays constant as the composition is changed over time.

Similar to ClinicalDocument/setId in CDA. See discussion in resource definition for how these relate.

A version-independent identifier for the Composition. This identifier stays constant as the composition is changed over time.

Similar to ClinicalDocument/setId in CDA. See discussion in resource definition for how these relate.

The purpose of this identifier.

Applications can assume that an identifier is permanent unless it explicitly says that it is temporary.

Identifies the purpose for this identifier, if known .

Allows the appropriate identifier for a particular context of use to be selected from among a set of identifiers.

Establishes the namespace for the value - that is, an absolute URL that describes a set values that are unique.

Identifier.system is always case sensitive. The FHIR specification, terminology.hl7.org and HL7 affiliates (for identifiers specific to their jurisdiction) define identifier systems that SHALL be used for certain types of identifiers. Specific rules can be found here.

There are many sets of identifiers. To perform matching of two identifiers, we need to know what set we're dealing with. The system identifies a particular set of unique identifiers.

The portion of the identifier typically relevant to the user and which is unique within the context of the system.

If the value is a full URI, then the system SHALL be urn:ietf:rfc:3986. The value's primary purpose is computational mapping. As a result, it may be normalized for comparison purposes (e.g. removing non-significant whitespace, dashes, etc.) A value formatted for human display can be conveyed using the http://hl7.org/fhir/StructureDefinition/rendered-value). Identifier.value is to be treated as case sensitive unless knowledge of the Identifier.system allows the processer to be confident that non-case-sensitive processing is safe.

An explicitly assigned identifier of a variation of the content in the Composition.

While each resource, including the composition itself, has its own version identifier, this is a formal identifier for the logical version of the Composition as a whole. It would remain constant if the resources were moved to a new server, and all got new individual resource versions, for example.

Workflow status of the guideline from registration to publication or deprecation. Please note that the ValueSet 'http://hl7.org/fhir/ValueSet/composition-status' is required; We therefore created the ConceptMap 'FHIRStatusToAWMFStatus' to store the mapping to the AWMF status values.

If a composition is marked as withdrawn, the compositions/documents in the series, or data from the composition or document series, should never be displayed to a user without being clearly marked as untrustworthy. The flag "entered-in-error" is why this element is labeled as a modifier of other elements.

Some reporting work flows require that the original narrative of a final document never be altered; instead, only new narrative can be added. The composition resource has no explicit status for explicitly noting whether this business rule is in effect. This would be handled by an extension if required.

The workflow/clinical status of the composition.

Need to be able to mark interim, amended, or withdrawn compositions or documents.

Specifies the particular kind of composition (e.g. History and Physical, Discharge Summary, Progress Note). This usually equates to the purpose of making the composition.

For Composition type, LOINC is ubiquitous and strongly endorsed by HL7. Most implementation guides will require a specific LOINC code, or use LOINC as an extensible binding.

Type of a composition.

Key metadata element describing the composition, used in searching/filtering.

A categorization for the type of the composition - helps for indexing and searching. This may be implied by or derived from the code specified in the Composition Type.

High-level kind of a clinical document at a macro level.

Helps humans to assess whether the composition is of interest when viewing an index of compositions or documents.

A categorization for the type of the composition - helps for indexing and searching. This may be implied by or derived from the code specified in the Composition Type.

High-level kind of a clinical document at a macro level.

Helps humans to assess whether the composition is of interest when viewing an index of compositions or documents.

A reference to a code defined by a terminology system.

Codes may be defined very casually in enumerations, or code lists, up to very formal definitions such as SNOMED CT - see the HL7 v3 Core Principles for more information. Ordering of codings is undefined and SHALL NOT be used to infer meaning. Generally, at most only one of the coding values will be labeled as UserSelected = true.

Allows for alternative encodings within a code system, and translations to other code systems.

The identification of the code system that defines the meaning of the symbol in the code.

The URI may be an OID (urn:oid:...) or a UUID (urn:uuid:...). OIDs and UUIDs SHALL be references to the HL7 OID registry. Otherwise, the URI should come from HL7's list of FHIR defined special URIs or it should be an absolute reference to some definition that establishes the system clearly and unambiguously.

Need to be unambiguous about the source of the definition of the symbol.

A symbol in syntax defined by the system. The symbol may be a predefined code or an expression in a syntax defined by the coding system (e.g. post-coordination).

Need to refer to a particular code in the system.

Modification date of the Composition contents. Does not represent the publication, last review or approval date.

The Last Modified Date on the composition may be after the date of the document was attested without being changed. This means that the date on an amended document is the date of the amendment, not the date of original authorship.

dateTime is used for tracking, organizing versions and searching. Note that this is the time of authoring this version of the Composition. When packaged in a document, Bundle.timestamp is the date of packaging.

The authors of the guildeline, either organizations or persons. Their respective role is defined by extension role: content-author, moderator etc.

Note that the authoring role defined here is disjunct with roles for the management of the guideline project as a whole (e.g., coordinatior, registrant etc). These are defined as dedicated contact points within the extension extendedContactDetail.

Identifies who is responsible for the content.

An Extension

Describes the role of the author of the guideline.

A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

Title of the guideline

For many compositions, the title is the same as the text or a display name of Composition.type (e.g. a "consultation" or "progress note"). Note that CDA does not make title mandatory, but there are no known cases where it is useful for title to be omitted, so it is mandatory here. Feedback on this requirement is welcome during the trial use period.

For any additional notes.

A comment, general note or annotation not coded elsewhere.

An Extension

The type of annotation. This extension can be used to map the v2 NTE-4 comment type field.

This is used to identify the type of annotation.

The text of the annotation in markdown format.

For any additional notes.

A comment, general note or annotation not coded elsewhere.

An Extension

The type of annotation. This extension can be used to map the v2 NTE-4 comment type field.

This is used to identify the type of annotation.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

The text of the annotation in markdown format.

A participant who has attested to the accuracy of the composition/document.

Only list each attester once.

Identifies responsibility for the accuracy of the composition content.

May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The type of attestation the authenticator offers.

Indicates the level of authority of the attestation.

A participant who has attested to the accuracy of the composition/document.

Only list each attester once.

Identifies responsibility for the accuracy of the composition content.

May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The type of attestation the authenticator offers.

Indicates the level of authority of the attestation.

Who attested the composition in the specified way.

Identifies who has taken on the responsibility for accuracy of the composition content.

A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

Relationships that this composition has with other compositions or documents (FHIR or non-FHIR resources) that already exist.

To reference (using relatesTo) a Bundle of type "document" or another Composition where you only have the identifier, use a targetReference with an identifier.
When a Composition is an alternate representation of another type of document e.g. CDA, the other document could be referenced in a DocumentReference resource.
Here is an example of using relatesTo to reference another Bundle of type "document" or Composition where you only have the identifier:

"relatesTo": [{
  "type": "replaces",
  "targetReference": {
    "identifier": { 
      "system": "...", 
      "value": "..."
    }
  } 
}]

Provides additional classifiers of the related artifact.

This extension defines a label for the 'relatesTo' relationship using a CodeableConcept.

May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The type of relationship to the related artifact.

The type of relationship to the related artifact.

The artifact that is related to this Composition Resource.

Relationships that this composition has with other compositions or documents (FHIR or non-FHIR resources) that already exist.

To reference (using relatesTo) a Bundle of type "document" or another Composition where you only have the identifier, use a targetReference with an identifier.
When a Composition is an alternate representation of another type of document e.g. CDA, the other document could be referenced in a DocumentReference resource.
Here is an example of using relatesTo to reference another Bundle of type "document" or Composition where you only have the identifier:

"relatesTo": [{
  "type": "replaces",
  "targetReference": {
    "identifier": { 
      "system": "...", 
      "value": "..."
    }
  } 
}]

Provides additional classifiers of the related artifact.

May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The type of relationship to the related artifact.

The type of relationship to the related artifact.

The artifact that is related to this Composition Resource.

Relationships that this composition has with other compositions or documents (FHIR or non-FHIR resources) that already exist.

To reference (using relatesTo) a Bundle of type "document" or another Composition where you only have the identifier, use a targetReference with an identifier.
When a Composition is an alternate representation of another type of document e.g. CDA, the other document could be referenced in a DocumentReference resource.
Here is an example of using relatesTo to reference another Bundle of type "document" or Composition where you only have the identifier:

"relatesTo": [{
  "type": "replaces",
  "targetReference": {
    "identifier": { 
      "system": "...", 
      "value": "..."
    }
  } 
}]

Provides additional classifiers of the related artifact.

May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The type of relationship to the related artifact.

The type of relationship to the related artifact.

The artifact that is related to this Composition Resource.

Relationships that this composition has with other compositions or documents (FHIR or non-FHIR resources) that already exist.

To reference (using relatesTo) a Bundle of type "document" or another Composition where you only have the identifier, use a targetReference with an identifier.
When a Composition is an alternate representation of another type of document e.g. CDA, the other document could be referenced in a DocumentReference resource.
Here is an example of using relatesTo to reference another Bundle of type "document" or Composition where you only have the identifier:

"relatesTo": [{
  "type": "replaces",
  "targetReference": {
    "identifier": { 
      "system": "...", 
      "value": "..."
    }
  } 
}]

Provides additional classifiers of the related artifact.

May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The type of relationship to the related artifact.

The type of relationship to the related artifact.