Attribute `attributeRelationship` cannot be required for MSD attributes

[hoehrmann]

Using https://github.com/sdmx-twg/sdmx-rest/blob/99e92fd7a7f2c1a0c5dcfb2776f2fdae3cf2458e/doc/data.md attributes=msd a SDMX-JSON data message would include metadata structure attributes as if they were datastructure attributes. MSD attributes do not define attribute relationships, but the attributeRelationship property is currently required for all attributes.

I think the property should be optional. Values cannot be provided in the attributes=msd case, and the information is only advisory anyway (when importing data from a SDMX-JSON data message, there does not seem a point in evaluating them and then wondering what to do if the relationships in the data message are different from those in the DSD). (I do not mind if REST API implementations are required to generate the property, when possible, but a data message should not become invalid due to the absence of the property).

(In doubt, please handle this as a public review comment on SDMX 3.1 once the comment period begins.)

[dosse]

Thanks for this feedback.

Currently, the documentation says:

This field is mandatory for data attributes but optional for referential metadata attributes and not to be supplied for measures or dimensions.

The schema does not require this property due to these different cases. Since this relationship is well-defined for DSD attributes, there should be no issue for web services to provide this information. This is what they already do anyway. And for a number of users, this is very important information, because it allows adapting the attributes layout in a web app accordingly.

[pedroacarranza]

@hoehrmann does @dosse 's comment above answers your question?