REST API Overview

SDMX Standard REST API Specification

Scope of the SDMX REST API

The RESTful API focuses on simplicity. The aim is not to replicate the full semantic richness of the SDMX-ML Query message but to make it simple to perform a limited set of standard queries. Also, in contrast to other parts of the SDMX specification, the RESTful API focuses solely on data retrieval (via HTTP GET). More specifically, the API allows:

• To retrieve structural metadata, using a combination of id, agencyID and version number.
• To retrieve statistical data or reference metadata using keys (with options for wildcarding and support for the OR operator), data or metadata flows and data or metadata providers.
• To further refine queries for statistical data or reference metadata using time information (start period and end period).
• To retrieve updates and revisions only.
• To return the results of a query in various formats. The desired format and version of the returned message will be specified using HTTP Content Negotiation (and the HTTP Accept request header).
• For structural metadata, it is possible to instruct the web service to resolve references (for instance, when querying for data structure definitions, it is possible to also retrieve the concepts and code lists used in the returned data structure definitions), as well as artefacts that use the matching artefact (for example, to retrieve the dataflows that use a matching data structure definition).
• For structural metadata, it is possible to retrieve a minimal version of the artefact, for the sake of efficiency (for example, to retrieve all code lists – names, ids, etc – without the codes).
• A distinction should be established between the elements that allow identifying the resource to be retrieved and the elements that give additional information about, or allow to further filter, the desired results. Elements belonging to the 1st category are specified in the path part of the URL while elements belonging to the 2nd category are specified in the query string part of the URL.

Implementation of the SDMX REST API in the Registry

The Registry is primarily concerned with structural metadata so implements a subset of the SDMX RESTful API specification.

SDMX REST API Function	Implemented
Structural Metadata Queries	YES
Schema Queries (for retrieving SDMX-ML Structure Specific Data validation schemas)	YES
Data Queries	NO
Data Availability	NO

The Registry API also provides some additional functions that are necessary for a practical registry implementation, but not explicitly provided for in SDMX standard REST specification.

Extended REST API Function	Purpose
Structure Submission	The addition or modification of structures using HTTP POST
Structure Deletion	Delete specific structures using HTTP DELETE
Data Validation (synchronous)	Validates a dataset submitted using HTTP POST returning a validation report in JSON
Data Transformation (synchronous)	Transforms a dataset submitted using HTTP POST to a different DSD with an optional report returned in JSON
Data Transformation and Validation (asynchronous)	Validates and transforms datasets asynchronously making it suitable for larger submissions
Product Info	Returns details about the running Registry Instance in JSON
Active User	Returns details about the current authenticated user in JSON

Structural Metadata Queries

A structural metadata query uses HTTP GET with the following general URL syntax:

http(s)://ws-entry-point/resource/agencyID/resourceID/version

Resources

The following resources are defined:

• datastructure (This has been shortened from DataStructureDefinition to allow for shorter URLs)
• metadatastructure (This has been shortened from MetadataStructureDefinition to allow for shorter URLs)
• categoryscheme
• conceptscheme
• codelist
• hierarchicalcodelist
• organisationscheme (The organisationscheme resource can be used whenever the role played by the organisation schemes is not known/relevant)
• agencyscheme (For 3 of the subtypes of OrganisationScheme, the id and version parameters have fixed values. See Section 03 of the SDMX information model document for additional information)
• dataproviderscheme
• dataconsumerscheme
• organisationunitscheme
• dataflow
• metadataflow
• reportingtaxonomy
• provisionagreement
• structureset
• process
• categorisation
• contentconstraint
• actualconstraint (a type of contentconstraint stating what data are actually present)
• allowedconstraint (a type of contentconstraint defining what data are allowed)
• attachmentconstraint
• transformationscheme
• rulesetscheme
• userdefinedoperatorscheme
• customtypescheme
• namepersonalisationscheme
• vtlmappingscheme
• structure (This type can be used to retrieve any type of structural metadata matching the supplied parameters)

Parameters

Parameters used for identifying a resource

The following parameters are used for identifying resources:

Parameter	Type	Description
agencyID	A string compliant with the SDMX common:NCNameIDType	The agency maintaining the artefact to be returned. It is possible to set more than one agency, using + as separator (e.g. BIS+ECB).
resourceID	A string compliant with the SDMX common:IDType	The id of the artefact to be returned. It is possible to set more than one id, using + as separator (e.g. CL_FREQ+CL_CONF_STATUS).
version	A string compliant with the SDMX common:VersionType	The version of the artefact to be returned. It is possible to set more than one version, using + as separator (e.g. 1.0+2.1).

The parameters mentioned above are specified using the following syntax:

protocol://ws-entry-point/resource/agencyID/resourceID/version

Furthermore, some keywords may be used:

Keywords	Scope	Description
all	agencyID	Returns artefacts maintained by any maintenance agency
all	resourceID	Returns all resources of the type defined by the resource parameter
all	version	Returns all versions of the resource
latest	version	Returns the latest version in production of the resource

As all is a reserved keyword in the SDMX RESTful API, it is recommended not to use it as an identifier for agencies, resources or a specific version.

The following rules apply:

• If no version is specified, the version currently used in production should be returned. It is therefore equivalent to using the keyword latest.
• If no agencyID is specified, the matching artefacts maintained by any maintenance agency should be returned. It is therefore equivalent to using the keyword all. This would potentially return more than one artefact, if different agencies give the same identifier to a resource (for example, http://ws-entry-point/codelist/all/CL_FREQ, could return more than one codelist if more than one agency is maintaining a codelist with id "CL_FREQ").
• If no resourceID is specified, all matching artefacts (according to the other criteria used) should be returned. It's is therefore equivalent to using the keyword all.
• If no parameters are specified, the latest version of all resources of the type identified by the resource parameter, maintained by any maintenance agency should be returned.

Additional parameter used for identifying a resource, for item scheme types

SDMX uses the item scheme pattern to model SDMX collections of items. These are:

• categoryscheme
• conceptscheme
• codelist
• organisationscheme
• agencyscheme
• dataproviderscheme
• dataconsumerscheme
• organisationunitscheme
• reportingtaxonomy
• transformationscheme
• rulesetscheme
• userdefinedoperatorscheme
• customtypescheme
• namepersonalisationscheme
• vtlmappingscheme

Although it is not following the item scheme pattern, hierarchicalcodelist is also a collection, i.e. a collection of hierarchies.

For these collections (those following the item scheme pattern or the hierarchicalcodelist), it is possible to use a 4th parameter for identifying a resource. The rules for the 3 other parameters, as defined in the section above, remain valid.

Parameter	Type	Description
itemID	A string compliant with the SDMX common:NestedNCNameIDType for conceptscheme and agencyscheme, SDMX common:IDType for hierarchicalcodelist or with the SDMX common:NestedIDType in all other cases	The id of the item to be returned. It is possible to set more than one id, using + as separator (e.g. A+Q+M).

This 4th parameter is used as follows:

protocol://ws-entry-point/resource/agencyID/resourceID/version/itemID

Furthermore, a keyword may be used:

Keyword	Scope	Description
all	itemID	Returns all items belonging to the item scheme

The following rules apply:

• If no itemID is specified, all the items belonging to the item scheme should be returned. It is therefore equivalent to using the keyword all.
• If itemID is set and is a top-level id (e.g.: Code A (Annual) in the Frequency Codelist), and such an item exists in the matching item scheme, the item scheme returned should contain only the matching item and its isPartial parameter should be set to true.
• If itemID is set and is a nested id (e.g.: Category A.1.1, belonging to Category A.1, belonging to Category A in a Category Scheme), and such an item exists in the matching item scheme, the item scheme returned should contain the matching item and its ancestors, and its isPartial parameter should be set to true.

Parameters used to further describe the desired results

The following parameters are used to further describe the desired results, once the resource has been identified. As mentioned in 3.2, these parameters appear in the query string part of the URL.

Parameter	Type	Description	Default
detail	String	This attribute specifies the desired amount of information to be returned. For example, it is possible to instruct the web service to return only basic information about the maintainable artefact (i.e.: id, agency id, version and name). Most notably, items of item schemes will not be returned (for example, it will not return the codes in a code list query). Possible values are: allstubs (all artefacts should be returned as stubs, containing only identification information, as well as the artefacts' name), referencestubs (referenced artefacts should be returned as stubs, containing only identification information, as well as the artefacts' name), referencepartial (referenced item schemes should only include items used by the artefact to be returned. For example, a concept scheme would only contain the concepts used in a DSD, and its isPartial flag would be set to true. Likewise, if a dataflow has been constrained, then the codelists referenced by the DSD referenced by the dataflow should only contain the codes allowed by the content constraint), allcompletestubs (all artefacts should be returned as complete stubs, containing identification information, the artefacts' name, description, annotations and isFinal information), referencecompletestubs (referenced artefacts should be returned as complete stubs, containing identification information, the artefacts' name, description, annotations and isFinal information) and full (all available information for all artefacts should be returned).	full
references	String	This attribute instructs the web service to return (or not) the artefacts referenced by the artefact to be returned (for example, the code lists and concepts used by the data structure definition matching the query), as well as the artefacts that use the matching artefact (for example, the dataflows that use the data structure definition matching the query). Possible values are: none (no references will be returned), parents (the artefacts that use the artefact matching the query), parentsandsiblings (the artefacts that use the artefact matching the query, as well as the artefacts referenced by these artefacts), children (artefacts referenced by the artefact to be returned), descendants (references of references, up to any level, will also be returned), all (the combination of parentsandsiblings and descendants). In addition, a concrete type of resource may also be used (for example, references=codelist).	none

Applicability and meaning of references attribute

The table below lists the 1st level artefacts (one level up, one level down) that will be returned if the references parameter is set to all. Artefacts referenced by the matching artefact are displayed in regular style, while the artefacts that reference the matching artefact are displayed in Italic.

Maintainable artefact	Artefacts returned
AgencyScheme	Categorisation, Process, MetadataStructureDefinition, StructureSet
Categorisation	All
CategoryScheme	Categorisations, Process, StructureSet
Codelist	Categorisation, Process, HierarchicalCodelist, ConceptScheme, DataStructureDefinition, MetadataStructureDefinition, StructureSet, VtlMappingScheme
ConceptScheme	Categorisation, Process, Codelist, DataStructureDefinition, MetadataStructureDefinition, StructureSet, VtlMappingScheme
Constraint	Categorisation, Process, DataProviderScheme, DataStructureDefinition, Dataflow, MetadataStructureDefinition, Metadataflow, ProvisionAgreement
DataConsumerScheme	Categorisation, Process, MetadataStructureDefinition, StructureSet
Dataflow	Categorisation, Process, Constraint, DataStructureDefinition, ProvisionAgreement, ReportingTaxonomy, StructureSet, VtlMappingScheme
DataProviderScheme	Categorisation, Process, Constraint, ProvisionAgreement, MetadataStructureDefinition, StructureSet
DataStructureDefinition	Categorisation, Process, Codelist, ConceptScheme, Constraint, Dataflow, StructureSet
HierarchicalCodelist	Categorisation, Process, Codelist, StructureSet
Metadataflow	Categorisation, Process, Constraint, MetadataStructureDefinition, ProvisionAgreement, ReportingTaxonomy, StructureSet
MetadataStructureDefinition	Categorisation, Process, ConceptScheme, Codelist, DataProviderScheme, DataConsumerScheme, AgencyScheme, OrganisationUnitScheme, Constraint, Metadataflow, StructureSet
OrganisationUnitScheme	Categorisation, Process, Constraint, MetadataStructureDefinition, StructureSet
Process	All
ProvisionAgreement	Categorisation, Process, DataProviderScheme, Dataflow, Metadataflow, Constraint
ReportingTaxonomy	Categorisation, Process, Dataflow, Metadataflow, StructureSet
StructureSet	Categorisation, Process, DataStructureDefinition, MetadataStructureDefinition, CategoryScheme, DataProviderScheme, DataConsumerScheme, AgencyScheme, OrganisationUnitScheme, ConceptScheme, Codelist, ReportingTaxonomy, HierarchicalCodelist, Dataflow, Metadataflow
CustomTypeScheme	AgencyScheme, Categorisation, TranformationScheme
NamePersonalisationScheme	AgencyScheme, Categorisation, TranformationScheme
RulesetScheme	AgencyScheme, Categorisation, TranformationScheme, VtlMappingScheme
TranformationScheme	AgencyScheme, Categorisation, CustomTypeScheme, NamePersonalisationScheme, RulesetScheme, UserDefinedOperatorScheme, VtlMappingScheme
UserDefinedOperatorScheme	AgencyScheme, Categorisation, TranformationScheme, VtlMappingScheme
VtlMappingScheme	AgencyScheme, Categorisation, Codelist, ConceptScheme, Dataflow, RulesetScheme, TranformationScheme, UserDefinedOperatorScheme

Examples

• To retrieve version 1.0 of the DSD with id ECB_EXR1 maintained by the ECB, as well as the code lists and the concepts used in the DSD:

  http://ws-entry-point/datastructure/ECB/ECB_EXR1/1.0?references=children&detail=referencepartial

• To retrieve the latest version in production of the DSD with id ECB_EXR1 maintained by the ECB, without the code lists and concepts of the DSD:

  http://ws-entry-point/datastructure/ECB/ECB_EXR1

• To retrieve all DSDs maintained by the ECB, as well as the dataflows using these DSDs:

  http://ws-entry-point/datastructure/ECB?references=dataflow

• To retrieve the latest version in production of all code lists maintained by all maintenance agencies, but without the codes:

  http://ws-entry-point/codelist?detail=allstubs

• To retrieve, as stubs, the latest version in production of all maintainable artefacts maintained by the ECB:

  http://ws-entry-point/structure/ECB?detail=allstubs

• To retrieve the category PRICES of the DOMAINS category scheme maintained by the ECB, as well as the categorisations referencing that category:

  http://ws-entry-point/categoryscheme/ECB/DOMAINS/latest/PRICES?references=categorisation

• To retrieve the latest version of the CL_FREQ codelists maintained by the BIS or the ECB: http://ws-entry-point/codelist/BIS+ECB/CL_FREQ</p></li></ul>

  Schema queries

  Resources

  The following resource is defined:

  • schema

  This resource allows a client to ask a service to return a schema, i.e. a document which defines data validity within a certain context. The service must take into account the constraints that apply within that context (DSD or MSD, dataflow or metadataflow, or provision agreement).

  This is typically used for validation purposes but it may also be used for communication purposes, i.e. as a way to inform providers about the data they are expected to report.

  Parameters

  Parameters used for identifying a resource

  The following parameters are used for identifying resources:

  Parameter	Type	Description
  context	One of the following: datastructure, metadatastructure, dataflow, metadataflow, provisionagreement	The value of this parameter determines the constraints that need to be taken into account, when generating the schema. If datastructure or metadatastructure is used, constraints attached to the DSD or MSD must be applied when generating the schema. If dataflow or metadataflow is used, constraints attached to the dataflow or metadataflow and to the DSD or MSD used in the dataflow or metadataflow must be applied when generating the schema. If provisionagreement is used, constraints attached to the provision agreement, as well as to the dataflow or metadafalow used in the agreement and the DSD or MSD used in the dataflow or metadataflow must be applied when generating the schema.
  agencyID	A string compliant with the SDMX common:NCNameIDType	The agency maintaining the artefact used to generate the schema to be returned.
  resourceID	A string compliant with the SDMX common:IDType	The id of the artefact used to generate the schema to be returned.
  version	A string compliant with the SDMX common:VersionType	The version of the artefact used to generate the schema to be returned.

  The parameters mentioned above are specified using the following syntax:

  protocol:// ws-entry-point/schema/context/agencyID/resourceID/version

  Furthermore, a keyword may be used:

  Keyword	Scope	Description
  latest	version	Returns the latest version in production of the resource

  As the query for schema must match one artefact only, the keyword all is not supported for agencyId and resourceId.

  The following rules apply:

  • If no version attribute is specified, the version currently used in production should be returned. It is therefore equivalent to using the keyword latest.

  Parameters used to further describe the desired results

  The following parameters are used to further describe the desired results, once the resource has been identified:

  Parameter	Type	Description
  dimensionAtObservation	A string compliant with the SDMX common:NCNameIDType	The ID of the dimension to be attached at the observation level.
  explicitMeasure	Boolean	For cross-sectional data validation, indicates whether observations are strongly typed (defaults to false).

  Using an SDMX format for the response

  By default, a schema query will return an XML schema (i.e. an xsd file). However, it is also possible to get the response in one of the SDMX Structure formats. In that case, the response should only include the following types of artefact: data structures, codelists, concept schemes and agency schemes. The various item schemes must only contain the following:

  • For codelists, the codes that are allowed after applying the constraints up to the specified context;
  • For concept schemes, the concepts that are used by the data structure;
  • For agency schemes, the agencies maintaining artefacts that are part of the response.

  Examples

  • To retrieve the schema for data supplied within the context of version 1.0 of the provision agreement EXR_WEB maintained by the ECB:

    http://ws-entry-point/schema/provisionagreement/ECB/EXR_WEB/1.0/

    In this case, the schema returned by the service must take into account the constraints attached to the provision agreement, the dataflow used in the provisionagreement and the data structure definition used in the dataflow.

  Structural Metadata Submission

  Structural metadata can be added or modified by using HTTP POST to submit any valid SDMX Structure Document to the secure API.

  Resource

  protocol://domain/ws/secure/sdmxapi/rest

  Example: https://registry.mydomain.org/FusionRegistry/ws/secure/sdmxapi/rest

  Authentication

  Only authenticated users with sufficient Agency or Admin privileges can modify structural metadata content. HTTP Basic Authentication must be used to with this service.

  Actions

  The following actions can be specified when submitting structural metadata content.

  Action	Behaviour
  Append	New maintainable structures are added, but an error occurs if any of the structures submitted already exist in the Registry
  Replace	Existing maintainable structures are replaced in their entirety and new ones added if needed
  Merge	Similar to Append except items are added to existing item schemes - useful for adding Codes to Codelists
  FullReplace	The entire contents of the Registry are replaced with the structures submitted
  Delete	The maintainables identified in the submitted content are deleted

  Submission Content Options

  The following SDMX Structure Documents can be submitted in the body of the POST:

  Message Type	Action
  SDMX-ML Structure Message	Specify the action using the HTTP 'Action' header (default is Replace)
  SDMX-JSON Structure Message	Specify the action using the HTTP 'Action' header (default is Replace)
  SDMX-EDI (GESMES) Structure Message	Specify the action using the HTTP 'Action' header (default is Replace)
  SDMX-ML SubmitStructureRequest Registry Interface Message	Specify the action using the 'Action' header in the message

  The content can be Zipped, and multi-part submissions are also accepted.

  Response

  A successful submission results in a SDMX-ML SubmitStructureResponse message. If an error occurs, a SDMX-ML ErrorResponseDocument is returned.

  Structure Deletion

  The simplest way to delete Structural Metadata is using the HTTP DELETE verb.

  Resources

  Deletion of structures uses the same resources as Structural Metadata Queries to identify precisely what to delete.

  Maintainables

  protocol://domain/ws/secure/sdmxapi/rest/resource/agencyID/resourceID/version

  Example:
  https://registry.mydomain.org/ws/secure/sdmxapi/rest/datastructure/ECB/ECB_TRD/1.0
  

  Items

  protocol://domain/ws/secure/sdmxapi/rest/resource/agencyID/resourceID/version/itemID

  Examples:
  https://registry.mydomain.org/ws/secure/sdmxapi/rest/codelist/ECB/CL_FREQ/1.0/A
  https://registry.mydomain.org/ws/secure/sdmxapi/rest/codelist/ECB/CL_FREQ/1.0/A+M+Q
  

  Authentication

  Only authenticated users with sufficient Agency or Admin privileges can modify structural metadata content. HTTP Basic Authentication must be used to with this service.

  Response

  A successful submission results in a SDMX-ML SubmitStructureResponse message. If an error occurs, a SDMX-ML ErrorResponseDocument is returned.