The TWG is planning to make a change to the SDMX Information Model in the next release of the standard. We are reaching out to the SDMX community to gather feedback about this change, in particular, practical use cases for which this change would represent an important issue.

Please send your feedback latest by 31-May-2024 to twg@sdmx.org

Proposed Change 
To reverse the relationship between the Allowed Data Constraint and the Constrained Structure (DSD, Dataflow, Provision Agreement, Data Provider).

In the current SDMX Information Model the Allowed Data Constraint contains the reference, this change will see this reference being removed from the Constraint and instead maintained in the Constrained Structure.

Impact Examples 
A Dataflow will contain the URN of the Constraint which is used to restrict its content.

The user can navigate from the Dataflow to the Constraint using the references ‘children’ or ‘descendants’ query parameter in the REST API.

Constraints can still be used to restrict content for multiple structures as there is no restriction on how many structures reference it.

Backwards and Forwards Compatibility 
The change will be backward-compatible in the sense that SDMX structure messages in previous format versions can be mapped 1-to-1 to messages in the new format versions.

The behaviour of the REST request with references=parents/descendants/children will behave in a manner consistent with the output format, i.e. an output in version 3.0 will treat the Dataflow as a child of the Constraint, in later versions this will reverse.

More details with examples is provided here: sdmx-im/proposals/003_constraint.md at 003_constraint_reversal · sdmx-twg/sdmx-im (github.com)