Path | Short | Definition | Comments |
---|---|---|---|
Definition of an operation or a named query | A formal computable definition of an operation (on the RESTful interface) or a named query (using the search interaction). | ||
url | Canonical identifier for this operation definition, represented as a URI (globally unique) | An absolute URI that is used to identify this operation 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 at which an authoritative instance of this operation definition is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the operation definition is stored on different servers. | 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](resource.html#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](resource.html#meta) element to indicate where the current master source of the resource can be found. |
version | Business version of the operation definition | The identifier that is used to identify this version of the operation definition when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the operation definition author and is not expected to be globally unique. For example, it might be a timestamp (e.g. yyyymmdd) if a managed version is not available. There is also no expectation that versions can be placed in a lexicographical sequence. | There may be different operation 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 operation definition with the format [url]|[version]. |
name | Name for this operation definition (computer friendly) | A natural language name identifying the operation definition. This name should be usable as an identifier for the module by machine processing applications such as 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. |
title | Name for this operation definition (human friendly) | A short, descriptive, user-friendly title for the operation definition. | This name does not need to be machine-processing friendly and may contain punctuation, white-space, etc. |
status | draft | active | retired | unknown | The status of this operation definition. Enables tracking the life-cycle of the content. | Allows filtering of operation definitions that are appropriate for use versus not. |
kind | operation | query | Whether this is an operation or a named query. | Named queries are invoked differently, and have different capabilities. |
experimental | For testing purposes, not real usage | A Boolean value to indicate that this operation definition is authored for testing purposes (or education/evaluation/marketing) and is not intended to be used for genuine usage. | Allows filtering of operation definitions that are appropriate for use versus not. |
date | Date last changed | The date (and optionally time) when the operation definition 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 operation definition changes. | Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the operation definition. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource. |
publisher | Name of the publisher (organization or individual) | The name of the organization or individual that published the operation definition. | Usually an organization but may be an individual. The publisher (or steward) of the operation definition is the organization or individual primarily responsible for the maintenance and upkeep of the operation 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 operation definition. This item SHOULD be populated unless the information is available from context. |
contact | Contact details for the publisher | 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. |
description | Natural language description of the operation definition | A free text natural language description of the operation definition from a consumer's perspective. | This description can be used to capture details such as why the operation definition 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 operation 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 operation definition is presumed to be the predominant language in the place the operation definition was created). |
useContext | The context that the content is intended to support | 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 operation definition instances. | When multiple useContexts are specified, there is no expectation that all or any of the contexts apply. |
jurisdiction | Intended jurisdiction for operation definition (if applicable) | A legal or geographic region in which the operation definition is intended to be used. | It may be possible for the operation definition to be used in jurisdictions other than those for which it was originally designed or intended. |
purpose | Why this operation definition is defined | Explanation of why this operation definition is needed and why it has been designed as it has. | This element does not describe the usage of the operation 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 operation definition. |
affectsState | Whether content is changed by the operation | Whether the operation affects state. Side effects such as producing audit trail entries do not count as 'affecting state'. | What http methods can be used for the operation depends on the .affectsState value and whether the input parameters are primitive or complex: 1. Servers SHALL support POST method for all operations. 2. Servers SHALL support GET method if all the parameters for the operation are primitive or there are no parameters and the operation has affectsState = false. |
code | Name used to invoke the operation | The name used to invoke the operation. | |
comment | Additional information about use | Additional information about how to use this operation or named query. | |
base | Marks this as a profile of the base | Indicates that this operation definition is a constraining profile on the base. | A constrained profile can make optional parameters required or not used and clarify documentation. |
resource | Types this operation applies to | The types on which this operation can be executed. | If the type is an abstract resource ("Resource" or "DomainResource") then the operation can be invoked on any concrete specialization. |
system | Invoke at the system level? | Indicates whether this operation or named query can be invoked at the system level (e.g. without needing to choose a resource type for the context). | |
type | Invoke at the type level? | Indicates whether this operation or named query can be invoked at the resource type level for any given resource type level (e.g. without needing to choose a specific resource id for the context). | |
instance | Invoke on an instance? | Indicates whether this operation can be invoked on a particular instance of one of the given types. | |
inputProfile | Validation information for in parameters | Additional validation information for the in parameters - a single profile that covers all the parameters. The profile is a constraint on the parameters resource as a whole. | If present the profile shall not conflict with what is specified in the parameters in the operation definition (max/min etc.), though it may provide additional constraints. The constraints expressed in the profile apply whether the operation is invoked by a POST wih parameters or not. |
outputProfile | Validation information for out parameters | Additional validation information for the out parameters - a single profile that covers all the parameters. The profile is a constraint on the parameters resource. | If present the profile shall not conflict with what is specified in the parameters in the operation definition (max/min etc.), though it may provide additional constraints. The constraints expressed in the profile apply whether the operation is invoked by a POST wih parameters or not. |
parameter | Parameters for the operation/query | The parameters for the operation/query. | Query Definitions only have one output parameter, named "result". This might not be described, but can be to allow a profile to be defined. |
parameter.id | Unique id for inter-element referencing | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces. | |
parameter.extension | Additional content defined by implementations | 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. |
parameter.modifierExtension | Extensions that cannot be ignored even if unrecognized | 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 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. 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. |
parameter.name | Name in Parameters.parameter.name or in URL | The name of used to identify the parameter. | This name must be a token (start with a letter in a..z, and only contain letters, numerals, and underscore. Note that for search parameters (type = string, with a search type), the name may be altered by the search modifiers. |
parameter.use | in | out | Whether this is an input or an output parameter. | If a parameter name is used for both an input and an output parameter, the parameter should be defined twice. |
parameter.min | Minimum Cardinality | The minimum number of times this parameter SHALL appear in the request or response. | |
parameter.max | Maximum Cardinality (a number or *) | The maximum number of times this element is permitted to appear in the request or response. | |
parameter.documentation | Description of meaning/use | Describes the meaning or use of this parameter. | |
parameter.type | What type this parameter has | The type for this parameter. | if there is no stated parameter, then the parameter is a multi-part parameter; type and must have at least one part defined. |
parameter.targetProfile | If type is Reference | canonical, allowed targets | Used when the type is "Reference" or "canonical", and identifies a profile structure or implementation Guide that applies to the target of the reference this parameter refers to. If any profiles are specified, then the content must conform to at least one of them. The URL can be a local reference - to a contained StructureDefinition, or a reference to another StructureDefinition or Implementation Guide by a canonical URL. When an implementation guide is specified, the target resource SHALL conform to at least one profile defined in the implementation guide. | Often, these profiles are the base definitions from the spec (e.g. http://hl7.org/fhir/StructureDefinition/Patient). |
parameter.searchType | number | date | string | token | reference | composite | quantity | uri | special | How the parameter is understood as a search parameter. This is only used if the parameter type is 'string'. | |
parameter.binding | ValueSet details if this is coded | Binds to a value set if this parameter is coded (code, Coding, CodeableConcept). | |
parameter.binding.id | Unique id for inter-element referencing | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces. | |
parameter.binding.extension | Additional content defined by implementations | 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. |
parameter.binding.modifierExtension | Extensions that cannot be ignored even if unrecognized | 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 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. 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. |
parameter.binding.strength | required | extensible | preferred | example | Indicates the degree of conformance expectations associated with this binding - that is, the degree to which the provided value set must be adhered to in the instances. | For further discussion, see [Using Terminologies](terminologies.html). |
parameter.binding.valueSet | Source of value set | Points to the value set or external definition (e.g. implicit value set) that identifies the set of codes to be used. | For value sets with a referenceResource, the display can contain the value set description. The reference may be version-specific or not. |
parameter.referencedFrom | References to this parameter | Identifies other resource parameters within the operation invocation that are expected to resolve to this resource. | Resolution applies if the referenced parameter exists. |
parameter.referencedFrom.id | Unique id for inter-element referencing | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces. | |
parameter.referencedFrom.extension | Additional content defined by implementations | 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. |
parameter.referencedFrom.modifierExtension | Extensions that cannot be ignored even if unrecognized | 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 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. 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. |
parameter.referencedFrom.source | Referencing parameter | The name of the parameter or dot-separated path of parameter names pointing to the resource parameter that is expected to contain a reference to this resource. | |
parameter.referencedFrom.sourceId | Element id of reference | The id of the element in the referencing resource that is expected to resolve to this resource. | |
parameter.part | Parts of a nested Parameter | The parts of a nested Parameter. | Query Definitions only have one output parameter, named "result". This might not be described, but can be to allow a profile to be defined. |
overload | Define overloaded variants for when generating code | Defines an appropriate combination of parameters to use when invoking this operation, to help code generators when generating overloaded parameter sets for this operation. | The combinations are suggestions as to which sets of parameters to use together, but the combinations are not intended to be authoritative. |
overload.id | Unique id for inter-element referencing | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces. | |
overload.extension | Additional content defined by implementations | 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. |
overload.modifierExtension | Extensions that cannot be ignored even if unrecognized | 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 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. 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. |
overload.parameterName | Name of parameter to include in overload | Name of parameter to include in overload. | |
overload.comment | Comments to go on overload | Comments to go on overload. |
The OperationDefinition resource provides a formal computable definition of an operation or a named query. The OperationDefinition serves two principal purposes:
See below for further information about these, and about how operations and named queries are executed.
OperationDefinitions are published to define operations that servers can implement in a common fashion. The FHIR specification itself describes some (see below), and other organizations (including IHE, national programs, jurisdictions and vendors) are able to publish additional OperationDefinitions.
OperationDefinition resources are referred to from two different places:
There are 2 ways to describe the input and output parameters for an operation:
OperationDefinition.parameter
to describe the parametersOperationDefinition.inputProfile
and OperationDefinition.outputProfile
The parameters is a simple list of possible parameters, along with cardinalities and types.
The profiles allow a rich set of validation rules etc. to be provided. OperationDefinitions SHALL
always define the parameters using OperationDefinition.parameter
in the resource,
and MAY also provide profiles for the parameters. If present, the profiles SHALL NOT disagree
with the parameters defined for the operation.
As an example, consider an operation that defines 3 parameters, 2 in and 1 out:
In Parameters: | |||||
Name | Cardinality | Type | Binding | Profile | Documentation |
a | 0..1 | integer | An integer parameter | ||
b | 0..1 | Patient | A patient parameter | ||
Out Parameters: | |||||
Name | Cardinality | Type | Binding | Profile | Documentation |
c | 1..1 | decimal | A result parameter |
In addition to specifying the operation parameters directly, an operation definition can also provide a profile:
"inputProfile" : "http://example.org/StructureDefinition/op.x.in.profile"
This profile would describe a parameters resource with 2 parameters (using slicing), with the same details as the table above. The operation definition would still list the parameters directly to save applications consuming the definition (e.g. to produce an OpenAPI document) from parsing and interpreting the profile.
OperationDefinitions with kind = operation
are executed as defined in the Operations Framework.
Named queries (OperationDefinitions with kind = query
) are executed by performing a search
with the value of the search parameter "_query" set to the name provided in the definition.
If the named query is to be performed over the RESTful API, all the parameters must be simple search parameters, so that they can be represented directly in the URL without tricky encoding issues. Named queries always return a bundle containing a set of resources, so all the out parameters must be resources, not data types.
For named queries, all the standard search parameters are automatically in scope (though servers do not need to support them unless explicitly documented).
There are two ways to pass resources to an operation: directly or by reference. The definition of an operation distinguishes between these two, since they have very different behaviors and consequences.
As an example, take the ValueSet.$expand operation. This operation takes a valueset as a direct parameter. The type of the parameter is defined as 'ValueSet'. In a Parameters resource, it would be represented like this:
<parameter> <name value="valueset"/> <resource> <ValueSet> <!-- Valueset contents --> </ValueSet> </resource> </parameter>
or, in JSON:
"parameter": [ { "name": "valueset", "resource": { "resourceType": "ValueSet", // Valueset contents } } ]
Other parameters are passed by reference. For example, the ChargeItemDefinition.$apply operation
takes two parameters of type Reference - one to the chargeItem and the other to the account. The type of the
parameters is Reference(Charge)
and Reference(Account)
, respectively. The expectation is that the server performing the
operation will resolve those references as part of the operation execution.
In a parameters resource, the chargeItem parameter would be represented like this:
<parameter> <name value="chargeItem"/> <valueReference> <reference value="ChargeItem/123"/> </valueReference> </parameter>
or, in JSON:
"parameter": [ { "name": "chargeItem", "valueReference" : { "reference" : "ChargeItem/123" } } ]
Some operations can take either form; in that case, two distinct parameters must be defined: one for a resource as a direct parameter, and one for a reference.
It is possible for two different organizations to create different operation definitions with the same name or, perhaps more likely, to define equivalent operations that have the same name but incompatible approaches in their parameter lists.
It is also possible, though unlikely, that a server will be required to support both of these operations. If this is the case, the server is able to do this by giving one of them a new name and referring to it by definition in the capability statement. To illustrate this, assume that two different organizations, "orgA" and "orgB", both define an operation called "dothis", and the definitions are incompatible. OrgA publishes its operation definition at http://orga.com/fhir/dothis.xml, and OrgB publishes its operation at http://fhir.orgb.com/meta/OperationDefinition/dothis. The server is able to implement both. Its capability statement will say:
<CapabilityStatement xmlns="http://hl7.org/fhir"> <!-- snip --> <rest> <!-- snip --> <operation> <name value="dothis"/> <definition> <reference value="http://orga.com/fhir/dothis.xml"/> </definition> </operation> <operation> <name value="dothis2"/> <definition> <reference value="http://fhir.orgb.com/meta/OperationDefinition/dothis"/> </definition> </operation> <!-- snip --> </rest> <!-- snip --> </CapabilityStatement>
If a general purpose cross server client is looking for the implementation of the http://fhir.orgb.com/meta/OperationDefinition/dothis operation and wants to be robust against this name clash problem, instead of simply executing the $dothis operation, it can look at the server's CapabilityStatement for the underlying definition URI and then execute the name given in the capability statement.
A client can determine the compatibility of the server by processing its capability statement and ensuring that the server implements the specific operation definitions and parameters required by the client. The client can then report a useful error to the user rather than allowing mystifying operational errors to occur.
However, there are fundamental limitations to this approach because there are many aspects of these operations that are not (or cannot be) defined in a formal fashion using OperationDefinition, for example, co-occurrence constraints among parameters.
In the same sense, a 3rd party tool can examine a server's CapabilityStatement and a client's definition of an acceptable server to determine whether those two system are interoperable or not.
Finally, it is possible to generate user interface forms automatically from
the OperationDefinition. The documentation in the OperationDefinition.description
and OperationDefinition.parameter.documentation
should be sufficient to allow
moderately technical users to guess at the correct content of the form.
For this reason, highly technical documentation should go in OperationDefinition.comment
.
It is anticipated that this would be used to automate development processes, rather than to generate end-user forms: such users will usually need more support than can be offered in a generated form.
base | Marks this as a profile of the base | OperationDefinition.base |
code | Name used to invoke the operation | OperationDefinition.code |
input-profile | Validation information for in parameters | OperationDefinition.inputProfile |
instance | Invoke on an instance? | OperationDefinition.instance |
kind | operation | query | OperationDefinition.kind |
output-profile | Validation information for out parameters | OperationDefinition.outputProfile |
system | Invoke at the system level? | OperationDefinition.system |
type | Invoke at the type level? | OperationDefinition.type |