YAML Schema Draft #1

gistfile1.yml

Field: !Mapping
    fields:
        type: # <--- that is name
            type:
            - string
            - TypesList
            optional: False # some explicid definition
        optional:
            type: boolean
            optional: True
            default: False
        default:
            type: object
            optional: True
            # do not define default for default

IntField: !Mapping
    extend: Field
    fields:
        type:
            # type is not defined because it was inherited
            optional: True
            default: int
        ge: # >=
            type: int
            optional: True
        gt: # >
            type: int
            optional: True
        eq: # ==
            type: int
            optional: True
        ne: # !=
            type: int
            optional: True
        le: # <
            type: int
            optional: True
        lt: # <=
            type: int
            optional: True

StringFields: !Mapping
    extend: Field
    fields:
        type:
            optional: True
            default: str

        min_length: !IntField
            optional: True
            ge: 0
            default: 0

        max_length: !IntField
            optional: True
            ge: 0

        regex: !StringFields
            optional: True
            regex: "^((?:(?:[^?+*{}()[\]\\|]+|\\.|\[(?:\^?\\.|\^[^\\]|[^\\^])(?:[^\]\\]+|\\.)*\]|\((?:\?[:=!]|\?<[=!]|\?>)?(?1)??\)|\(\?(?:R|[+-]?\d+)\))(?:(?:[?+*]|\{\d+(?:,\d*)?\})[?+]?)?|\|)*)$"

Idetifier: !StringFields
    min_length: 1
    regex: "^[^\d\W]\w*$"

TypesList: !List
    min_length: 1
    item_type: string

Rule: !Mapping
    fields:
        extend:
            type:
            - string
            - TypesList
            optional: True

List: !Mapping
    extend: Rule
    fields:
        min_length: !IntField
            optional: True
            ge: 0
            default: 0
            
        max_length: !IntField
            optional: True
            ge: 0
            
        item_type: !IntField
            type:
            - string
            - TypesList
            optional: False

PairPattern: !Mapping
    fields:
        key:
            type:
            - string
            - TypesList
            optional: True
        value:
            type:
            - string
            - TypesList
            optional: True

FieldsMap: !Mapping
    patterns:
    -
        key: Identifier
        value: Field

Mapping: !Mapping
    extend: Rule
    fields:
        fields:
            type: FieldsMap
            optional: True
        patterns: !List
            item_type: PairPattern
            min_length: 1
            optional: True