tosca_definitions_version: tosca_simple_yaml_1_0_0
node_types: 
  tosca.nodes.BlockStorage:
    derived_from: tosca.nodes.Root
    properties:
      size: 
        type: scalar-unit.size
        constraints:
          - greater_or_equal: 1 MB
      volume_id:
        type: string
        required: false
      snapshot_id:
        type: string
        required: false
    capabilities:
      attachment: 
        type: tosca.capabilities.Attachment