SDMX technical standards – bis.org

The BIS hosts nine international organisations engaged in standard setting and the pursuit of financial stability through the Basel Process.
In this section:
The SDMX Technical Specification formally defines the standard and has four main parts.
The SDMX information model is a standardised object model for modelling statistical domains centring on the structure of the data sets, the coding schemes used for classifying series, and the rules for controlling the exchange of data. The model also allows for the definition of various business rules including those for checking data quality and transforming their structures and classification schemes. Means of categorising and indexing the data are provided to help end users such as subject-matter statisticians discover the datasets and series they need.
When implementing statistical systems based on the SDMX standard, this “structural metadata” can be used to drive all stages of the data life cycle, from the reporting, collection, validation and transformation stages to dissemination.
A simplified high-level version of the SDMX information model is shown below.

The web services application programming interface (API) specification provides a standardised interface for interacting with software systems implementing the SDMX standard.
The BIS SDMX API web service offers programmatic access to data and metadata published on the BIS statistics pages. The related open API documentation describes the supported functionality in an interactive way. Data retrieval and discovery are supported in a variety of formats (eg JSON, XML, CSV).
Data and structural metadata are available via this REST API service. Examples of usage are also illustrated in the REST API pages for data, data availability and structures (like DSDs, Codelists, Concept Schemes).
The web service complies with the SDMX 2.1 RESTful specification. Part of the standard is a Wiki on the SDMX RESTful specification, published on GitHub. It covers topics such as data retrieval, content negotiation and possible status codes. If you are a user of the BIS SDMX API web service, we recommend that you read the Wiki list of tips.
SDMX 2.1 supports transmission of data and structural metadata in EDI, XML and JSON formats, and of data only using CSV. XML and JSON also support reference metadata. EDI will be  deprecated in version 3.0, but the BIS supports all versions of SDMX and therefore will continue to support EDI as a data transmission format.
An SDMX registry is a controlled repository for structural metadata and processes, which organisations can consult for information on how to structure, process, validate and interpret statistical data. For example, a central bank that reports the international banking statistics to the BIS could consult the relevant registry to find out how the data set should be structured and its series classified.
The SDMX Global Registry  is operated by the SDMX sponsors and holds metadata describing the structure (ie DSDs) for a number of global standard data sets, including those for the European system of national accounts and the UN’s Sustainable Development Goals.
The current version 2.1 was released in 2011, and was followed by incremental enhancements. Version 3.0, scheduled for release in late 2021, includes improvements derived from a decade of experience with the current version. New features, such as support for geospatial classifications and micro data, have been added, and some parts of the standard, now considered obsolete, have been removed.

source