An Attribute is a general purpose class from which different subtypes can be derived. Each such subtype should then be serialized using the serialization of the Attribute class, which means that all that it should add to the serialization is the version number.

Attributes are used in COMSOL Multiphysics for internal purposes, and these attributes are not documented. However, because Attribute has a strict serialization structure, the serialization of these attributes is well documented.