---
rootElement: { presence: required, structure: {
  field1: {
    presence: required,
    comment: "field 1 description",
    structure: {
      field11:{
        presence: required,
        comment: "field 11 description"
      },
      field12: {
        presence: required,
        comment: "field 12 description"
      },
      field13: {
        presence: optional,
        value: [ X, Y, Z ],
        comment: "field 13 description"
      }
    }
  },
  field2: {
    presence: required,
    comment: "field 2 description"
  },
  field3: {
    presence: required,
    value: [ 3, 30, 33 ],
    comment: "field 2 description"
  }
}}
...
---
rootElement:
  field1:
    field11: test11
    field12: test12
    field13: A
  field2: test2
  field3: 3
...
---
rootElement:
  field1:
    field11: test11
    field12: test12
  field2: test2
  field3: 300
...
---
rootElement:
  field1:
    field11: test11
    field12: test12
  field3: 3
...