Allowed values for x-v and x-min-v

Question

In descriptions of endpoint parameters, such as CDS Banking APIs, the x-v and x-min-v request header Type property is string. In CDS HTTP Headers, the x-v and x-min-v request header  Description property states that they "must be set to a positive integer". Which is correct?

The second question is about response header parameter x-v. If the required API version is 1, and the request header contains x-v=0001, what are the status of the request and the required response:

• Request is valid and response header is x-v=1
• Request is invalid and response is 400 Bad Request
• Request is valid and response header is x-v=0001

Answer

The requirement is to populate the x-v and x-min-v headers with positive integer values. Technically, all headers are strings.  Unlike in the JSON specification, the HTTP specification does not make a distinction for headers between numbers and strings.  

If the request header contains x-v=0001, the best response is to treat the request as valid and returnx-v=1. A good, tolerant server implementation allows any technically correct request. The standards do not require leading zeroes for a positive integer but do not preclude leading zeroes. Treating this as an error would be an over-interpretation and not aligned with the intent. If you are building an ADR solution, however, the DSB does not recommend using leading zeroes in the x-vand x-min-v values.