Added response section

spec/Appendix B -- Variable Batching.md

@@ -50,10 +50,90 @@ A _variable batching request_ follows the same structure as a standard GraphQL r
 - {extensions} - (_Optional_, map): This entry is reserved for implementors to
  extend the protocol however they see fit.
 
-#### Response Media Type
+### Accept
 
-A **variable batching request** by default use the `Content-Type: application/graphql+jsonl` header for its responses. This indicates that the request body is formatted in JSON Lines, where each line represents the response for a single set of variables.
+A client SHOULD indicate the media types that it supports in responses using the `Accept` HTTP header as specified in [RFC7231](https://datatracker.ietf.org/doc/html/rfc7231).
 
+For **variable batching requests**, the client SHOULD include the media type `application/graphql+jsonl` in the `Accept` header to indicate that it expects a batched response in JSON Lines format.
 
+If the client supplies an Accept header, the client SHOULD include the media type `application/graphql+jsonl` in the Accept header.
 
+If the client does not supply an `Accept` header, the server MAY respond with a default content type of `application/graphql+jsonl`, or it may use any other media type it supports. However, to ensure compatibility and clarity, it is RECOMMENDED that the client explicitly states its preferred media types using the `Accept` header.
 
+### POST
+
+A **variable batching request** instructs the server to perform a query or mutation operation multiple times, once for each set of variables provided. The request MUST have a body that contains the values of the _variable batching request_ parameters encoded in the `application/graphql+jsonl` media type, or another media type supported by the server.
+
+A client MUST indicate the media type of a request body using the `Content-Type` header as specified in [RFC7231](https://datatracker.ietf.org/doc/html/rfc7231).
+
+A server MUST support POST requests encoded with the `application/json` media type (as outlined in the GraphQL-over-HTTP specification).
+
+If the client does not supply a `Content-Type` header with a POST request, the server SHOULD reject the request using the appropriate `4xx` status code.
+
+### JSON Encoding
+
+When encoded in JSON, a _GraphQL-over-HTTP request_ is encoded as a JSON object
+(map), with the properties specified by the GraphQL-over-HTTP request:
+
+- {query} - the string representation of the Source Text of the Document as
+ specified in
+ [the Language section of the GraphQL specification](https://spec.graphql.org/draft/#sec-Language).
+- {operationName} - an optional string
+- **{variables}** - An array of JSON objects (maps), where each map corresponds to a set of variables to be used in the query.
+ names and the values of which are the variable values
+- {extensions} - an optional object (map)
+
+#### Example
+
+If we wanted to execute the following GraphQL query:
+
+```raw graphql example
+query ($id: ID!) {
+ user(id: $id) {
+ name
+ }
+}
+```
+
+With the following query variable sets:
+
+```json example
+[
+ {
+ "id": "QVBJcy5ndXJ1"
+ },
+ {
+ "id": "QVBJcy5ndXJ2"
+ },
+ {
+ "id": "QVBJcy5ndXJ3"
+ }
+]
+```
+
+This request could be sent via an HTTP POST to the relevant URL using the JSON
+encoding with the headers:
+
+```headers example
+Content-Type: application/json
+Accept: application/graphql-response+jsonl
+```
+
+And the body:
+
+```json example
+{
+ "query": "query ($id: ID!) {\n user(id: $id) {\n name\n }\n}",
+ "variables": [
+ {
+ "id": "QVBJcy5ndXJ1"
+ },
+ {
+ "id": "QVBJcy5ndXJ2"
+ },
+ {
+ "id": "QVBJcy5ndXJ3"
+ }
+ ]
+}
+```