Typically a Method is defined on an ObjectType having the ModellingRule Optional or Mandatory. Such a Method then also appears optionally or mandatorily on the Objects of the ObjectType.

Methods defined on an ObjectType may have the ModellingRule OptionalPlaceholder or MandatoryPlaceholder. In this case, the ObjectType does not define the input and output arguments, but just the name of the Method. Instances can then use an appropriate signature. This approach should only be used when the signature cannot be standardized.

ObjectTypes may also have Methods without a ModellingRule. In this case, it is a class Method called on the ObjectType. In 8.4.1, an example is given, where such a class Method creates instances of the ObjectType.