This is a translation of the JSDL sample from the JSON Description Language http://area.autodesk.com/blogs/chris/json-scene-description-language. You can copy paste the following YAML grammar on an online YAML parser (like http://yaml-online-parser.appspot.com/ )

JSDL1.yaml

# YAML Version of the JSDL Autodesk example http://area.autodesk.com/blogs/chris/json-scene-description-language
# This version is using flow nodes [ ] { } like JSON but is less verbose by removing all double quotes
{
  id: my_scene,
  roots: [  
    {
      assets: [Square],
      children: [ 
        {
          transform:
          [
             1, 0, 0, 3,
             0, 1, 0, 4,
             0, 0, 1, 5,
             0, 0, 0, 1
          ],
          assets: [Square],
        }
      ],
    }
  ],
  assets: [
    Square: {
      representations: [
        threejs.geometry.json, 
        wavefront.obj, 
        alembic],
      default: { 
        type: threejs.geometry.json,
        value: {
            vertexes: [
                [-1, 1, 0],
                [1, 1, 0],
                [1, -1, 0],
                [-1, -1, 0],
            ],
            faces: [
                [3, 2, 1],
                [3, 1, 0],
            ]
        }
      }    
    }
  ]
}

JSDL2.yaml

# YAML Version of the JSDL Autodesk example http://area.autodesk.com/blogs/chris/json-scene-description-language
# This version is using whitespace structured document (as python) mixed with some inline lists []
id: my_scene,
roots:
  - assets: [Square]
    children:
      - transform:
          [
             1, 0, 0, 3,
             0, 1, 0, 4,
             0, 0, 1, 5,
             0, 0, 0, 1
          ]
        assets: [Square]
assets:
  - Square:
      representations:
        - threejs.geometry.json, 
        - wavefront.obj, 
        - alembic
      default:
        type: threejs.geometry.json,
        value:
          vertexes: [
              [-1, 1, 0],
              [1, 1, 0],
              [1, -1, 0],
              [-1, -1, 0],
          ]
          faces: [
              [3, 2, 1],
              [3, 1, 0],
          ]

JSDLOriginal.json

{
  "id" : "my_scene"
  "roots" : [  
    { 
      "assets" : ["Square"],
      "children" : 
      [
         "transform" : 
         [
            1, 0, 0, 3,
            0, 1, 0, 4,
            0, 0, 1, 5,
            0, 0, 0, 1
         ]
         "assets" : ["Square"],
      ],
    }
  ],
  "assets" : [
    "Square" : {
        "representations" : [
           "threejs.geometry.json", 
           "wavefront.obj", 
           "alembic"],
        "default" : { 
            "type" : "threejs.geometry.json",
            "value" : {
                "vertexes" : [
                    [-1, 1, 0],
                    [1, 1, 0],
                    [1, -1, 0],
                    [-1, -1, 0],
                ],
                "faces": [
                    [3, 2, 1],
                    [3, 1, 0],
                ]
            }
        }    
    }  
}