Fix: #1366. Include Mark's feedback.

draft-ietf-httpbis-digest-headers.md

@@ -538,45 +538,38 @@ To allow sender and recipient to provide a checksum which is independent from
     * Status: standard
 
 
-# Use of Digest when acting on resources {#acting-on-resources}
+# Using Digest in State-Changing Requests {#state-changing-requests}
 
-POST and PATCH requests can appear to convey partial representations but are
-semantically acting on resources. The enclosed representation, including its
-metadata, refers to that action.
-
-In these requests the representation digest MUST be computed on the
-representation-data of that action.
+When the representation enclosed in a state-changing request
+does not describe the target resource,
+the representation digest MUST be computed on the
+representation-data.
 This is the only possible choice because representation digest requires complete
 representation metadata (see {{representation-digest}}).
 
 In responses,
 
 - if the representation describes the status of the request,
   `Digest` MUST be computed on the enclosed representation
-   (see {{post-referencing-action}} );
+   (see {{post-referencing-status}} );
 
 - if there is a referenced resource
   `Digest` MUST be computed on the selected representation of the referenced resource
    even if that is different from the target resource.
    That might or might not result in computing `Digest` on the enclosed representation.
 
-The latter case might be done according to the HTTP semantics of the given
+The latter will be done according to the HTTP semantics of the given
 method, for example using the `Content-Location` header field.
 In contrast, the `Location` header field does not affect `Digest` because
 it is not representation metadata.
 
-## Digest and PATCH
-
-In PATCH requests, the representation digest MUST be computed on the patch document
+For example, in PATCH requests, the representation digest
+will be computed on the patch document
 because the representation metadata refers to the patch document and not
 to the target resource (see Section 2 of {{?PATCH=RFC5789}}).
-
-In PATCH responses, the representation digest MUST be computed on the selected
+In responses instead, the representation digest will be computed on the selected
 representation of the patched resource.
 
-`Digest` usage with PATCH is thus very similar to POST, but with the
-resource's own semantic partly implied by the method and by the patch document.
-
 ## Digest and Content-Location in Responses {#digest-and-content-location}
 
 When a state-changing method returns the `Content-Location` header field, the
@@ -889,7 +882,7 @@ Note that a `204 No Content` response without content but with the same
 `Digest` field-value would have been legitimate too.
 In that case, `Content-Digest` would have been computed on an empty content.
 
-## POST Response Describes the Request Status {#post-referencing-action}
+## POST Response Describes the Request Status {#post-referencing-status}
 
 The request `Digest` field-value is computed on the enclosed representation (see
 {{acting-on-resources}}).