• value @ url

A free text natural language description of the laboratory procedure from a consumer's perspective.

Examples could be lab specialties: chemistry, hormonology, hematology, bacteriology, virology .. Other examples might list medical specialty of orderer: cardiology, dermatology, gastroenterology ...

• value @ system

Identifies the facility where the laboratory procedure will occur, and where the specimens will be conveyed

May be tha laboratory as a whole or its work area facility or a sector of it

Defines specimen requirements for the laboratory procedure (test or panel) to be performed.

Defines observation requirements for the laboratory procedure (test or panel) to be performed, such as body weight or surface area.

Defines the observations that are expected to be produced by the laboratory procedure.

An Extension

• value @ url

Language translation from base language of resource to another language.

A free text natural language description of the laboratory procedure from a consumer's perspective.

Examples could be lab specialties: chemistry, hormonology, hematology, bacteriology, virology .. Other examples might list medical specialty of orderer: cardiology, dermatology, gastroenterology ...

• value @ system

Identifies the facility where the laboratory procedure will occur, and where the specimens will be conveyed

May be tha laboratory as a whole or its work area facility or a sector of it

Defines specimen requirements for the laboratory procedure (test or panel) to be performed.

Defines observation requirements for the laboratory procedure (test or panel) to be performed, such as body weight or surface area.

Defines the observations that are expected to be produced by the laboratory procedure.

This resource allows for the definition of some activity to be performed, independent of a particular patient, practitioner, or other performance context.

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

Within the context of the FHIR RESTful interactions, the resource has an id except for cases like the create and conditional update. Otherwise, the use of the resouce id depends on the given use case.

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.

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).

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 a 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, 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.

May be used to represent additional information that is not part of the basic definition of the resource. 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.

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.

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).

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 activity definition 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 an authoritative instance of this activity definition is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the activity definition is stored on different servers.

Allows the activity 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 activity 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 activity 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 activity definition when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the activity 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. 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 assets.

There may be different activity 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 activity 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 activity 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 activity definition.

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

unique id for the element within a resource (for internal references)

An Extension

• value @ url

Language translation from base language of resource to another language.

The actual value

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

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

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

See guidance around (not) making local changes to elements here.

A Boolean value to indicate that this activity 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 activity definition.

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

A code, group definition, or canonical reference that describes or identifies the intended subject of the activity being defined. Canonical references are allowed to support the definition of protocols for drug and substance quality specifications, and is allowed to reference a MedicinalProductDefinition, SubstanceDefinition, AdministrableProductDefinition, ManufacturedItemDefinition, or PackagedProductDefinition resource.

Note that the choice of canonical for the subject element was introduced in R4B to support pharmaceutical quality use cases. To ensure as much backwards-compatibility as possible, it is recommended to only use the new canonical type with these use cases.

The date (and optionally time) when the activity 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 activity 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 activity definition. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource.

See guidance around (not) making local changes to elements here.

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

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

Usually an organization but may be an individual. The publisher (or steward) of the activity definition is the organization or individual primarily responsible for the maintenance and upkeep of the activity 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 activity 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.

See guidance around (not) making local changes to elements here.

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 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.

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 name of an individual to contact.

If there is no named individual, the telecom information is for the organization as a whole.

The contact details for the individual (if a name was provided) or the organization.

A free text natural language description of the laboratory procedure 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 activity 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 activity definition is presumed to be the predominant language in the place the activity 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 activity 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 activity definition is intended to be used.

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

DEPRECATION NOTE: For consistency, implementations are encouraged to migrate to using the new 'jurisdiction' code in the useContext element. (I.e. useContext.code indicating http://terminology.hl7.org/CodeSystem/usage-context-type#jurisdiction and useContext.valueCodeableConcept indicating the jurisdiction.)

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

This element does not describe the usage of the activity 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 activity definition.

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

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

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

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 will 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 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.

See guidance around (not) making local changes to elements here.

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.

See guidance around (not) making local changes to elements here.

The period during which the activity definition 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 activity definition are or are expected to be used instead.

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

See guidance around (not) making local changes to elements here.

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 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.

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 start of the period. The boundary is inclusive.

If the low element is missing, the meaning is that the low boundary is not known.

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.

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

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

Examples could be lab specialties: chemistry, hormonology, hematology, bacteriology, virology .. Other examples might list medical specialty of orderer: cardiology, dermatology, gastroenterology ...

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 asserted by the publisher to be primarily responsible for review of some aspect of the content.

See guidance around (not) making local changes to elements here.

An individual or organization asserted by the publisher to be responsible for officially endorsing the content for use in some setting.

See guidance around (not) making local changes to elements here.

Related artifacts such as additional documentation, justification, or bibliographic references.

Activity definitions must be able to provide enough information for consumers of the content (and/or interventions or results produced by the content) to be able to determine and understand the justification for and evidence in support of the content.

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

A reference to a Library resource containing any formal logic used by the activity definition.

A description of the kind of resource the activity definition is representing. For example, a MedicationRequest, a ServiceRequest, or a CommunicationRequest.

The kind element may only specify Request resource types to facilitate considering user input as part of processing the result of any automated clinical reasoning processes. To support creation of event resources, such as Observations, RiskAssessments, and DetectedIssues, use a Task resource with the focus of the task set to the event resource to be created. Note that the kind of resource to be created may determine what types of extensions are permitted.

A profile to which the target of the activity definition is expected to conform.

Allows profiles to be used to describe the types of activities that can be performed within a workflow, protocol, or order set.

Detailed description of the type of activity; e.g. What lab test, what procedure, what kind of encounter.

Allows matching performed to planned as well as validation against protocols.

Tends to be less relevant for activities involving particular products.

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 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.

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 reference to a code defined by a terminology system.

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

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.

• value @ system

A reference to a code defined by a terminology system.

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

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.

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 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.

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

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

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.

The version of the code system which was used when choosing this code. Note that a well-maintained code system does not need the version reported, because the meaning of codes is consistent across versions. However this cannot consistently be assured, and when the meaning is not guaranteed to be consistent, the version SHOULD be exchanged.

Where the terminology does not clearly define what string should be used to identify code system versions, the recommendation is to use the date (expressed in FHIR date format) on which that version was officially published as the version date.

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.

A representation of the meaning of the code in the system, following the rules of the system.

Need to be able to carry a human-readable meaning of the code for readers that do not know the system.

Indicates that this coding was chosen by a user directly - e.g. off a pick list of available items (codes or displays).

This has been identified as a clinical safety criterium - that this exact system/code pair was chosen explicitly, rather than inferred by the system based on some rules or language processing.

Amongst a set of alternatives, a directly chosen code is the most appropriate starting point for new translations. There is some ambiguity about what exactly 'directly chosen' implies, and trading partner agreement may be needed to clarify the use of this element and its consequences more completely.

A human language representation of the concept as seen/selected/uttered by the user who entered the data and/or which represents the intended meaning of the user.

The codes from the terminologies do not always capture the correct meaning with all the nuances of the human using them, or sometimes there is no appropriate code at all. In these cases, the text is used to capture the full meaning of the source.

Very often the text is the same as a displayName of one of the codings.

Indicates the level of authority/intentionality associated with the activity and where the request should fit into the workflow chain.

Indicates how quickly the activity should be addressed with respect to other requests.

Set this to true if the definition is to indicate that a particular activity should NOT be performed. If true, this element should be interpreted to reinforce a negative coding. For example NPO as a code with a doNotPerform of true would still indicate to NOT perform the action.

This element is not intended to be used to communicate a decision support response to cancel an order in progress. That should be done with the "remove" type of a PlanDefinition or RequestOrchestration.

The timing or frequency upon which the described activity is to occur.

Allows prompting for activities and detection of missed planned activities.

The intent of the timing element is to provide timing when the action should be performed. As a definitional resource, this timing is interpreted as part of an apply operation so that the timing of the result actions in a CarePlan or RequestOrchestration, for example, would be specified by evaluating the timing definition in the context of the apply and setting the resulting timing on the appropriate elements of the target resource. If the timing is an Age, the activity is expected to be performed when the subject is the given Age. When the timing is a Duration, the activity is expected to be performed within the specified duration from the apply. When the timing is a Range, it may be a range of Ages or Durations, providing a range for the expected timing of the resulting activity. When the timing is a Timing, it is establishing a schedule for the timing of the resulting activity.

If a CodeableConcept is present, it indicates the pre-condition for performing the service. For example "pain", "on flare-up", etc.

Identifies the facility where the laboratory procedure will occur, and where the specimens will be conveyed

Helps in planning of activity.

May be tha laboratory as a whole or its work area facility or a sector of it

Indicates who should participate in performing the action described.

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 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.

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.

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).

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.

The type of participant in the action.

The type of participant in the action.

The type of participant in the action.

When this element is a reference, it SHOULD be a reference to a definitional resource (for example, a location type, rather than a specific location).

The role the participant should play in performing the described action.

Indicates how the actor will be involved in the action - author, reviewer, witness, etc.

Identifies the food, drug or other product being consumed or supplied in the activity.

Identifies the quantity expected to be consumed at once (per dose, per meal, etc.).

Provides detailed dosage instructions in the same way that they are described for MedicationRequest resources.

If a dosage instruction is used, the definition should not specify timing or quantity.

Indicates the sites on the subject's body where the procedure should be performed (I.e. the target sites).

Knowing where the procedure is made is important for tracking if multiple sites are possible.

Only used if not implicit in the code found in ServiceRequest.type.

Defines specimen requirements for the laboratory procedure (test or panel) to be performed.

Needed to represent lab order definitions.

Defines observation requirements for the laboratory procedure (test or panel) to be performed, such as body weight or surface area.

Needed to represent observation definitions.

Defines the observations that are expected to be produced by the laboratory procedure.

A reference to a StructureMap resource that defines a transform that can be executed to produce the intent resource using the ActivityDefinition instance as the input.

Note that if both a transform and dynamic values are specified, the dynamic values will be applied to the result of the transform.

Dynamic values that will be evaluated to produce values for elements of the resulting resource. For example, if the dosage of a medication must be computed based on the patient's weight, a dynamic value would be used to specify an expression that calculated the weight, and the path on the request resource that would contain the result.

Dynamic values are applied in the order in which they are defined in the ActivityDefinition. Note that if both a transform and dynamic values are specified, the dynamic values will be applied to the result of the transform.

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 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.

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.

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).

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.

The path to the element to be customized. This is the path on the resource that will hold the result of the calculation defined by the expression. The specified path SHALL be a FHIRPath resolvable on the specified target type of the ActivityDefinition, and SHALL consist only of identifiers, constant indexers, and a restricted subset of functions. 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).

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

An expression specifying the value of the customized element.

The expression may be inlined, or may be a reference to a named expression within a logic library referenced by the library element.