1. Format transformation:
   Client (JSON) → Gateway → Backend (XML)

2. Protocol translation:
   Client (REST) → Gateway → Backend (gRPC)

3. Field mapping:
   Client (userId) → Gateway → Backend (user_id)

4. Aggregation:
   Client → Gateway → [Backend A, Backend B] → Gateway → Client

// Client sends JSON:
Request:  {"type": "api_request", "msg_id": 1, "method": "POST", "path": "/api/users", "headers": {"Content-Type": "application/json"}, "body": {"name": "Alice", "email": "alice@example.com"}}

// Gateway transforms to XML and sends to backend:
Backend Request:  {"method": "POST", "path": "/users", "headers": {"Content-Type": "application/xml"}, "body": "<?xml version="1.0"?><user><name>Alice</name><email>alice@example.com</email></user>"}

// Backend responds with XML:
Backend Response:  {"status": 201, "body": "<?xml version="1.0"?><user><id>123</id><name>Alice</name><email>alice@example.com</email></user>"}

// Gateway transforms to JSON and sends to client:
Response: {"type": "api_response", "in_reply_to": 1, "status": 201, "body": {"id": 123, "name": "Alice", "email": "alice@example.com"}}

{
  "transformations": {
    "/api/users": {
      "request": {
        "field_mappings": {
          "userId": "user_id",
          "firstName": "first_name",
          "lastName": "last_name"
        },
        "format": "json_to_xml"
      },
      "response": {
        "field_mappings": {
          "user_id": "userId",
          "first_name": "firstName",
          "last_name": "lastName"
        },
        "format": "xml_to_json"
      }
    }
  }
}