This standard uses the ModellingRules OptionalPlaceholder and MandatoryPlaceholder to define instance declarations, and defines a rule that the BrowseName of instance declarations having an OptionalPlaceholder or MandatoryPlaceholder ModellingRule be enclosed in angle brackets (<>). Originally, this rule is defined in OPC 10000-3 as a recommendation. This naming rule is also used in the description of a table. The BrowseName of a Node that has OptionalPlaceholder or MandatoryPlaceholder ModellingRule are described with angle brackets, which denotes that the name is not fixed. For example, BrowseName of Property is described as <PropertyName> in graphical notation and tables results in a Property that can have any name.