The subsequent table (see e.g. table 2.2. for nouns) shows the type hierarchy of the category, displaying the hierarchical relationships between subcategories and the morphosyntactic features which are applicable to them. The table appears subdivided into two zones. There is no hierarchical relation between features of the second zone; they cross-classify the feature space.
In such a way, constraints in the application of an attribute or a value - or a set of attributes or values - in presence of a given attribute or value are specified (e.g. common Gender does not apply to proper nouns or, Person with all its values does not apply to Non-finite forms in Italian verbs, table 3.2).
Why a typed hierarchy has been
chosen? That has been considered a good mean to translate
dependencies and constraints between features and values
into a formalism - which makes use of Type
Feature Structures (TFS) -, and to handle them with rigorous
computational techniques rather than leaving them to a human control.