MarkDto.json

{
  "id": 1,
  "value": 5.0,
  "weight": 2.0,
  "groupId": 1
}

MarkGroup.json

 {
   "id": 1,
   "value": 5.5,
   "weight": 1.0,
   "marks": [
     {
       "id": 1,
       "value": 5.0,
       "weight": 2.0,
       "groupId": 1
     }
   ],
   "subjectId": 3,     //one of the parents has to be 0
   "parentGroupId": 0,
   "markGroups": []
 }

SemesterMarkDto.json

{
  "id": 1,
  "name": "1. Semester",
  "validFrom": "2017-01-01",
  "validTo": "2017-06-30",
  "subjects": [
    {
      "id": 1,
      "name": "Math",
      "color": "...",
      "subjectMarkGroup": {
        "id": 1,
        "value": 5.5,
        "weight": 1.0,
        "marks": [
          {
            "id": 2,
            "value": 5.0,
            "weight": 2.0,
            "groupId": 2
          }
        ],
        "markGroups": [
          {
            "id": 2,
            "value": 5.5,
            "weight": 1.0,
            "marks": [
              {
                "id": 1,
                "value": 5.0,
                "weight": 2.0,
                "groupId": 1
              }
            ],
            "markGroups": [],
            "subjectId": 0,
            "parentGroupId": 1
          }
        ],
        "subjectId": 1,
        "parentGroupId": 0  
      }
    }
  ]
}