Important characteristics of the Arabic adjectival system are investigated, in view of the question of how the DP system is organized. A first series of issues include: (a) how adjective serialization observes quasi-universal hierarchical ordering restrictions (or their mirror image order), (b) how adjectives and other modifiers and determiners alternate in postnominal and prenominal positions, and (c) how distributional classes of adjectives relate to attributive/predicative, or head/modifier uses. A second series concerns (d) inflectional properties of adjectives (including Case, Definiteness, and Number and Gender features), and their Head/Spec dependent status. Such questions are approached through postulating an articulated (fissioned) DP structure. Structural grounds are provided for checking various inflectional features in hierarchically ordered, but autonomous DP domains. AP (or A) movement, as well as N and Possessor raisings, are independently motivated. Cross-linguistic variation follows, depending on whether all, some, or none of these processes are involved, to yield convergent derivations. APs (along with NPs) are treated as DPs, taking into account their inflectional and interpretational behaviours. Definiteness inheritance and Genitive checking are reanalyzed in view of new empirical and theoretical considerations of synthetic possessive structures.