027-Clarity-Status code for SDMX error 150?

[dosse]

In 4_7_errors.md, shouldn't the HTTP status code for the SDMX error 150 "Semantic error" not be "422 Unprocessable Entity" (rather than currently "403 Forbidden")?

The SDMX description is:

   Semantic error - 150
   A web service should return this error when a request is 
   syntactically correct but fails a semantic validation or 
   violates agreed business rules.

See https://tools.ietf.org/html/rfc4918#section-11.2 :

   The 422 (Unprocessable Entity) status code means the server
   understands the content type of the request entity (hence a
   415(Unsupported Media Type) status code is inappropriate), and the
   syntax of the request entity is correct (thus a 400 (Bad Request)
   status code is inappropriate) but was unable to process the contained
   instructions.  For example, this error condition may occur if an XML
   request body contains well-formed (i.e., syntactically correct), but
   semantically erroneous, XML instructions."

A sub-question:
How should the server behave if a data query contains valid and invalid codes in the key parameter? Should the service return the available data only for the valid codes and ignore the others, or refuse the execution and return an SDMX 150 error? This would be worthwhile to be clarified in the standard so that client applications can expect a consistent behaviour.

[sosna]

Findings

Proposed code 422:

• Semantically more correct;
• Already used in popular APIs (e.g. Twitter, GitHub);
• Not part of RFC 7231 (HTTP/1.1), upon which the initial mapping was based, but part of RFC 4918 (WebDav);
• Not part of the JAX-RS Enum listing common status codes (i.e. the Java API for RESTful web services);
• Not part of System.Net HttpStatusCode Enum;
• Part of ASP.NET Core StatusCodes class;
• Part of Python HTTPStatus;

Open question: Would this break backward compatibility?