Deep linguistic processing is a research-intensive area with several potential applications. Amidst the vast literature on formal linguistic theory, Head- driven Phrase Structure Grammar (HPSG) has a unique position, since it combines the best features of the contemporary approaches as well as establishes an integrated framework for cross-layer representation of linguistic objects. There is very few HPSG analysis of Arabic morphological, syntactic and semantic features. Arabic is the best instance of nonconcatenative morphology among the living languages. Arabic verb system shows a rich morphology, capable of lexically expressing diverse syntactic and semantic phenomena. Formalisms of existing morphological analyzers for Arabic cannot capture this higher layer diversity due to a lack of mathematical rigor and expressiveness. In this book, we discuss the HPSG framework to support rich nonconcatenative morphology of Arabic verbs. We present HPSG analysis of the agency of Arabic passives and reflexives as well as morphologically complex predication of causatives in accordance with the existing analysis in other languages.