L0 = <http://www.simantics.org/Layer0-1.1>

DATA = <http://www.simantics.org/Datatypes-1.1>

DATA.BTree <T L0.Entity
  >-- DATA.BTree.root --> DATA.BTreeNode <R L0.IsComposedOf : L0.FunctionalRelation
  >-- DATA.BTree.t --> L0.Integer <R L0.HasProperty : L0.FunctionalRelation
  >-- DATA.BTree.HasOwnerRelation <R L0.DependsOn
  >-- DATA.BTree.HasNodeType <R L0.DependsOn
  >-- DATA.BTree.mod --> L0.Long <R L0.HasProperty : L0.FunctionalRelation

DATA.BTreeNode <T L0.Entity
  >-- DATA.BTreeNode.content --> DATA.BTreeNode.Content <R L0.HasProperty : L0.FunctionalRelation
  >-- DATA.BTreeNode.Owns <R L0.IsComposedOf
    L0.InverseOf DATA.BTreeNode.IsOwnedBy

DATA.BTreeNode.Content <T L0.Literal
    @L0.assert L0.HasDataType ${ 
      leaf : Boolean,
      size : Integer,
      keys : Optional(Variant)[],
      values : Optional(Long(unit="resource"))[],
      children : Optional(Long(unit="resource"))[] 
    }