Properties are Server-defined characteristics of Objects, DataVariables and other Nodes. Properties differ from Attributes in that they characterise what the Node represents, such as a device or a purchase order. Attributes define additional metadata that is instantiated for all Nodes from a NodeClass. Attributes are common to all Nodes of a NodeClass and only defined by this specification whereas Properties can be Server-defined.

For example, an Attribute defines the DataType of Variables whereas a Property can be used to specify the engineering unit of some Variables.

To prevent recursion, Properties are not allowed to have Properties defined for them. To easily identify Properties, the BrowseName of a Property shall be unique in the context of the Node containing the Properties (see 5.6.3 for details).

A Node and its Properties shall always reside in the same Server.