Merge pull request #4130 from handrews/resolve-304

Note relative URL-reference resolution ambiguity

Author: handrews

versions/3.0.4.md

@@ -231,10 +231,13 @@ OpenAPI Description authors SHOULD consider how text using such extensions will
 ### Relative References in URLs
 
 Unless specified otherwise, all fields that are URLs MAY be relative references as defined by [RFC3986](https://tools.ietf.org/html/rfc3986#section-4.2).
+
 Relative references are resolved using the URLs defined in the [Server Object](#server-object) as a Base URI.
 
 Relative references used in `$ref` are processed as per [JSON Reference](https://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03), using the URL of the current document as the base URI. See also the [Reference Object](#reference-object).
 
+It is _implementation_defined_ whether the resolution of relative references in each of the `operationRef` field of the [Link Object](#link-object), the URI form of the `mapping` field of the [Discriminator Object](#discriminator-object), the `externalValue` field of the [Example Object](#example-object), and the `url` fields of the [External Documentation](#external-documentation-object), [Contact](#contact-object), and [License](#license-object) Objects resolve by using the same process as `$ref` or by using the Server Object.  For compatibility with future versions of this specification, the `$ref` process is RECOMMENDED for all of these fields.
+
 Relative references in CommonMark hyperlinks are resolved in their rendered context, which might differ from the context of the API description.
 
 ### Schema