Any required libraries, terminologies, or other artifacts that must be present in a run-time context.

An executable library must specify any required dependencies.

• value @ contentType

An executable library must specify its content in an executable form.

An executable library must specify its content in an executable form.

A comment containing additional documentation, a review comment, usage guidance, or other relevant information from a particular user.

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.

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.

Any required libraries, terminologies, or other artifacts that must be present in a run-time context.

An executable library must specify any required dependencies.

A FHIR Query URL pattern that corresponds to the data specified by the data requirement. If multiple FHIR Query URLs are present, they each contribute to the data specified by the data requirement (i.e. the union of the results of the FHIR Queries represents the complete data for the data requirement). This is not a resolveable URL, in that it will contain 1) No base canonical (i.e. it's a relative query), and 2) Parameters using tokens that are delimited using double-braces and the context parameters are dependent solely on the subjectType, according to the following: Patient: context.patientId, Practitioner: context.practitionerId, Organization: context.organizationId, Location: context.locationId, Device: context.deviceId.

Supports communicating a FHIR query (or set of queries) for the given data requirement. The query is server-specific, and will need to be created as informed by a CapabilityStatement. The $data-requirements operation should be expected to be able to provide an Endpoint or CapabilityStatement to provide this information.; If no endpoint or capability statement is provided, the capability statement of the server performing the operation is used.

• value @ contentType

An executable library must specify its content in an executable form.

An executable library must specify its content in an executable form.

The Library resource is a general-purpose container for knowledge asset definitions. It can be used to describe and expose existing knowledge assets such as logic libraries and information model descriptions, as well as to describe a collection of knowledge assets.

The logical id of the resource, as used in the URL for the resource. Once assigned, this value never changes.

The only time that a resource does not have an id is when it is being submitted to the server using a create operation.

The metadata about the resource. This is content that is maintained by the infrastructure. Changes to the content might not always be associated with version changes to the resource.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

The version specific identifier, as it appears in the version portion of the URL. This value changes when the resource is created, updated, or deleted.

The server assigns this value, and ignores what the client specifies, except in the case that the server is imposing version integrity on updates/deletes.

When the resource last changed - e.g. when the version changed.

This value is always populated except when the resource is first being created. The server / resource manager sets this value; what a client provides is irrelevant. This is equivalent to the HTTP Last-Modified and SHOULD have the same value on a read interaction.

A uri that identifies the source system of the resource. This provides a minimal amount of Provenance information that can be used to track or differentiate the source of information in the resource. The source may identify another FHIR server, document, message, database, etc.

In the provenance resource, this corresponds to Provenance.entity.what[x]. The exact use of the source (and the implied Provenance.entity.role) is left to implementer discretion. Only one nominated source is allowed; for additional provenance details, a full Provenance resource should be used.

This element can be used to indicate where the current master source of a resource that has a canonical URL if the resource is no longer hosted at the canonical URL.

A list of profiles (references to StructureDefinition resources) that this resource claims to conform to. The URL is a reference to StructureDefinition.url.

It is up to the server and/or other infrastructure of policy to determine whether/how these claims are verified and/or updated over time. The list of profile URLs is a set.

Security labels applied to this resource. These tags connect specific resources to the overall security policy and infrastructure.

The security labels can be updated without changing the stated version of the resource. The list of security labels is a set. Uniqueness is based the system/code, and version and display are ignored.

Tags applied to this resource. Tags are intended to be used to identify and relate resources to process and workflow, and applications are not required to consider the tags when interpreting the meaning of a resource.

The tags can be updated without changing the stated version of the resource. The list of tags is a set. Uniqueness is based the system/code, and version and display are ignored.

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 it's 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).

A human-readable narrative that contains a summary of the resource and can be used to represent the content of the resource to a human. The narrative need not encode all the structured data, but is required to contain sufficient detail to make it "clinically safe" for a human to just read the narrative. Resource definitions may define what content should be represented in the narrative to ensure clinical safety.

Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded information is added later.

These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, and nor can they have their own independent transaction scope.

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.

An Extension

• value @ url

A comment containing additional documentation, a review comment, usage guidance, or other relevant information from a particular user.

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 manageable, 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).

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.

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.

An absolute URI that is used to identify this library when it is referenced in a specification, model, design or an instance; also called its canonical identifier. This SHOULD be globally unique and SHOULD be a literal address at which at which an authoritative instance of this library is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the library is stored on different servers.

Allows the library 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 library when it is represented in other formats, or referenced in a specification, model, design or an instance. e.g. CMS or NQF identifiers for a measure artifact. Note that at least one identifier is required for non-experimental active artifacts.

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 library outside of FHIR, where it is not possible to use the logical URI.

The identifier that is used to identify this version of the library when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the library 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. To provide a version consistent with the Decision Support Service specification, use the format Major.Minor.Revision (e.g. 1.0.0). For more information on versioning knowledge assets, refer to the Decision Support Service specification. Note that a version is required for non-experimental active artifacts.

There may be different library 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 library with the format [url]|[version].

A natural language name identifying the library. 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 library.

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

An explanatory or alternate title for the library giving additional information about its content.

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

Allows filtering of libraries that are appropriate for use vs. not.

A Boolean value to indicate that this library 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 library.

Allows filtering of librarys that are appropriate for use versus not.

Identifies the type of library such as a Logic Library, Model Definition, Asset Collection, or Module Definition.

A code or group definition that describes the intended subject of the contents of the library.

The date (and optionally time) when the library was published. 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 library changes.

Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the library. 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 that published the library.

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

Usually an organization but may be an individual. The publisher (or steward) of the library is the organization or individual primarily responsible for the maintenance and upkeep of the library. 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 library. 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 library from a consumer's perspective.

This description can be used to capture details such as why the library was built, comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the library 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 library is presumed to be the predominant language in the place the library 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 library 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 library is intended to be used.

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

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

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

A detailed description of how the library is used from a clinical perspective.

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

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

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

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

The date on which the resource content was last reviewed. Review happens periodically after approval but does not change the original approval date.

Gives a sense of how "current" the content is. Resources that have not been reviewed in a long time may have a risk of being less appropriate/relevant.

If specified, this date follows the original approval date.

The period during which the library content was or is planned to be in active use.

Allows establishing a transition before a resource comes into effect and also allows for a sunsetting process when new versions of the library are or are expected to be used instead.

The effective period for a library 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 might be published in 2015.

Descriptive topics related to the content of the library. Topics provide a high-level categorization of the library that can be useful for filtering and searching.

Repositories must be able to determine how to categorize the library so that it can be found by topical searches.

An individiual or organization primarily involved in the creation and maintenance of the content.

An individual or organization primarily responsible for internal coherence of the content.

An individual or organization primarily responsible for review of some aspect of the content.

An individual or organization responsible for officially endorsing the content for use in some setting.

Any required libraries, terminologies, or other artifacts that must be present in a run-time context.

An executable library must specify any required dependencies.

Each related artifact is either an attachment, or a reference to another resource, but not both.

The parameter element defines parameters used by the library.

Describes a set of data that must be provided in order to be able to successfully perform the computations defined by the library.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

A FHIR Query URL pattern that corresponds to the data specified by the data requirement. If multiple FHIR Query URLs are present, they each contribute to the data specified by the data requirement (i.e. the union of the results of the FHIR Queries represents the complete data for the data requirement). This is not a resolveable URL, in that it will contain 1) No base canonical (i.e. it's a relative query), and 2) Parameters using tokens that are delimited using double-braces and the context parameters are dependent solely on the subjectType, according to the following: Patient: context.patientId, Practitioner: context.practitionerId, Organization: context.organizationId, Location: context.locationId, Device: context.deviceId.

Supports communicating a FHIR query (or set of queries) for the given data requirement. The query is server-specific, and will need to be created as informed by a CapabilityStatement. The $data-requirements operation should be expected to be able to provide an Endpoint or CapabilityStatement to provide this information.; If no endpoint or capability statement is provided, the capability statement of the server performing the operation is used.

The type of the required data, specified as the type name of a resource. For profiles, this value is set to the type of the base resource of the profile.

The profile of the required data, specified as the uri of the profile definition.

The intended subjects of the data requirement. If this element is not provided, a Patient subject is assumed.

The subject of a data requirement is critical, as the data being specified is determined with respect to a particular subject. This corresponds roughly to the notion of a Compartment in that it limits what data is available based on its relationship to the subject. In CQL, this corresponds to the context declaration.

Indicates that specific elements of the type are referenced by the knowledge module and must be supported by the consumer in order to obtain an effective evaluation. This does not mean that a value is required for this element, only that the consuming system must understand the element and be able to provide values for it if they are available.

The value of mustSupport SHALL be a FHIRPath resolveable on the type of the DataRequirement. The path SHALL consist only of identifiers, constant indexers, and .resolve() (see the Simple FHIRPath Profile for full details).

Code filters specify additional constraints on the data, specifying the value set of interest for a particular element of the data. Each code filter defines an additional constraint on the data, i.e. code filters are AND'ed, not OR'ed.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

The code-valued attribute of the filter. The specified path SHALL be a FHIRPath resolveable on the specified type of the DataRequirement, and SHALL consist only of identifiers, constant indexers, and .resolve(). The path is allowed to contain qualifiers (.) to traverse sub-elements, as well as indexers ([x]) to traverse multiple-cardinality sub-elements (see the Simple FHIRPath Profile for full details). Note that the index must be an integer constant. The path must resolve to an element of type code, Coding, or CodeableConcept.

The path attribute contains a Simple FHIRPath Subset that allows path traversal, but not calculation.

A token parameter that refers to a search parameter defined on the specified type of the DataRequirement, and which searches on elements of type code, Coding, or CodeableConcept.

The valueset for the code filter. The valueSet and code elements are additive. If valueSet is specified, the filter will return only those data items for which the value of the code-valued element specified in the path is a member of the specified valueset.

The codes for the code filter. If values are given, the filter will return only those data items for which the code-valued attribute specified by the path has a value that is one of the specified codes. If codes are specified in addition to a value set, the filter returns items matching a code in the value set or one of the specified codes.

Date filters specify additional constraints on the data in terms of the applicable date range for specific elements. Each date filter specifies an additional constraint on the data, i.e. date filters are AND'ed, not OR'ed.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

The date-valued attribute of the filter. The specified path SHALL be a FHIRPath resolveable on the specified type of the DataRequirement, and SHALL consist only of identifiers, constant indexers, and .resolve(). The path is allowed to contain qualifiers (.) to traverse sub-elements, as well as indexers ([x]) to traverse multiple-cardinality sub-elements (see the Simple FHIRPath Profile for full details). Note that the index must be an integer constant. The path must resolve to an element of type date, dateTime, Period, Schedule, or Timing.

The path attribute contains a Simple FHIR Subset that allows path traversal, but not calculation.

A date parameter that refers to a search parameter defined on the specified type of the DataRequirement, and which searches on elements of type date, dateTime, Period, Schedule, or Timing.

The value of the filter. If period is specified, the filter will return only those data items that fall within the bounds determined by the Period, inclusive of the period boundaries. If dateTime is specified, the filter will return only those data items that are equal to the specified dateTime. If a Duration is specified, the filter will return only those data items that fall within Duration before now.

Specifies a maximum number of results that are required (uses the _count search parameter).

Enables the requirement "most recent 5 results" to be expressed.

This element can be used in combination with the sort element to specify quota requirements such as "the most recent 5" or "the highest 5".

Specifies the order of the results to be returned.

Enables the requirement "most recent 5 results" to be expressed.

This element can be used in combination with the sort element to specify quota requirements such as "the most recent 5" or "the highest 5". When multiple sorts are specified, they are applied in the order they appear in the resource.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

The attribute of the sort. The specified path must be resolvable from the type of the required data. The path is allowed to contain qualifiers (.) to traverse sub-elements, as well as indexers ([x]) to traverse multiple-cardinality sub-elements. Note that the index must be an integer constant.

The direction of the sort, ascending or descending.

The content of the library as an Attachment. The content may be a reference to a url, or may be directly embedded as a base-64 string. Either way, the contentType of the attachment determines how to interpret the content.

• value @ contentType

The content of the library as an Attachment. The content may be a reference to a url, or may be directly embedded as a base-64 string. Either way, the contentType of the attachment determines how to interpret the content.

An executable library must specify its content in an executable form.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

Identifies the type of the data in the attachment and allows a method to be chosen to interpret or render the data. Includes mime type parameters such as charset where appropriate.

Processors of the data need to be able to know how to interpret the data.

The human language of the content. The value can be any valid value according to BCP 47.

Users need to be able to choose between the languages in a set of attachments.

The actual data of the attachment - a sequence of bytes, base64 encoded.

The data needs to able to be transmitted inline.

The base64-encoded data SHALL be expressed in the same character set as the base resource XML or JSON.

A location where the data can be accessed.

The data needs to be transmitted by reference.

If both data and url are provided, the url SHALL point to the same content as the data contains. Urls may be relative references or may reference transient locations such as a wrapping envelope using cid: though this has ramifications for using signatures. Relative URLs are interpreted relative to the service url, like a resource reference, rather than relative to the resource itself. If a URL is provided, it SHALL resolve to actual data.

The number of bytes of data that make up this attachment (before base64 encoding, if that is done).

Representing the size allows applications to determine whether they should fetch the content automatically in advance, or refuse to fetch it at all.

The number of bytes is redundant if the data is provided as a base64binary, but is useful if the data is provided as a url reference.

The calculated hash of the data using SHA-1. Represented using base64.

Included so that applications can verify that the contents of a location have not changed due to technical failures (e.g., storage rot, transport glitch, incorrect version).

The hash is calculated on the data prior to base64 encoding, if the data is based64 encoded. The hash is not intended to support digital signatures. Where protection against malicious threats a digital signature should be considered, see Provenance.signature for mechanism to protect a resource with a digital signature.

A label or set of text to display in place of the data.

Applications need a label to display to a human user in place of the actual data if the data cannot be rendered or perceived by the viewer.

The date that the attachment was first created.

This is often tracked as an integrity issue for use of the attachment.

The content of the library as an Attachment. The content may be a reference to a url, or may be directly embedded as a base-64 string. Either way, the contentType of the attachment determines how to interpret the content.

An executable library must specify its content in an executable form.

Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, 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.

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.

• value @ url

Identifies the type of the data in the attachment and allows a method to be chosen to interpret or render the data. Includes mime type parameters such as charset where appropriate.

Processors of the data need to be able to know how to interpret the data.

The human language of the content. The value can be any valid value according to BCP 47.

Users need to be able to choose between the languages in a set of attachments.

The actual data of the attachment - a sequence of bytes, base64 encoded.

The data needs to able to be transmitted inline.

The base64-encoded data SHALL be expressed in the same character set as the base resource XML or JSON.

A location where the data can be accessed.

The data needs to be transmitted by reference.

If both data and url are provided, the url SHALL point to the same content as the data contains. Urls may be relative references or may reference transient locations such as a wrapping envelope using cid: though this has ramifications for using signatures. Relative URLs are interpreted relative to the service url, like a resource reference, rather than relative to the resource itself. If a URL is provided, it SHALL resolve to actual data.

The number of bytes of data that make up this attachment (before base64 encoding, if that is done).

Representing the size allows applications to determine whether they should fetch the content automatically in advance, or refuse to fetch it at all.

The number of bytes is redundant if the data is provided as a base64binary, but is useful if the data is provided as a url reference.

The calculated hash of the data using SHA-1. Represented using base64.

Included so that applications can verify that the contents of a location have not changed due to technical failures (e.g., storage rot, transport glitch, incorrect version).

The hash is calculated on the data prior to base64 encoding, if the data is based64 encoded. The hash is not intended to support digital signatures. Where protection against malicious threats a digital signature should be considered, see Provenance.signature for mechanism to protect a resource with a digital signature.

A label or set of text to display in place of the data.

Applications need a label to display to a human user in place of the actual data if the data cannot be rendered or perceived by the viewer.

The date that the attachment was first created.

This is often tracked as an integrity issue for use of the attachment.