Rudder

On system group detail, we always have the text

Hierarchy of group and unicity of property name

A group property with a given name can be defined in several group if and only if these groups are in a sub-group hierarchical relation. A group 'S' is a subgroup of group 'P' if 'S' uses the 'AND' operand with the 'Group > Group ID = P' criterion.
Property inheritance and overriding in hierarchy

When a group is a subgroup of another one, it inherit all its properties. If it defines a property with the same name than a parent, then that property value is overriden and the subgroup value is used. A node can also define a property with the same name, and in that case its value will override any group's value for that property name.
Overriding order between several parents

If a group is a subgroup of several groups, then the overriding is done in the same order than groups are defined in criteria lines: the last group define the group whose value will be chosen among parents.