Any node or any class that has been defined can also be assigned an arbitrary
property. Properties can be used to define behavioral aspects that span over
several classes and/or nodes. A node may only belong to one class, but it can have as many properties as desired.
PROPERTY property_name
[-c class[,class]...] [-n node[,node]...]
[-r range] [-re regexp]
Defines a property that applies to the given nodes/classes.
property_name is any alphanumeric string to be used to reference the property.
-c grants the property to all nodes in the given classes.
-n grants the property to the given nodes.
-r grants the property to all nodes matching the given node range.
-re grants the property to all nodes matching the given regular expression.