Categorizing features
Section 5.3.4 describes how to categorize features using subclasses.
It is not clear why there is a third option to create categories apart from creating subclasses of Feature of Interest and Feature Kind.
In the example 1 given, Window should be a subclass of FeatureOfInterest and not of Feature.
In example 3, it is not clear why all office rooms are offices or systems.
It is not clear which requirements lead to this restriction or if this comes from some extension.