Dialectology is the study of dialects, which are varieties of a language spoken by groups smaller than the total community of speakers of the language. These varieties differ along many dimensions of “language content, structure and function” (Francis (1983:1).This variation concerns the lexicon, pronunciation, grammar, usage, social function, artistic and literary expression. There is no language without variation. The latter can be either incidental or systematic. In the first case, variation affects individual linguistic items without seriously annoying the system, whereas in the second, language is greatly affected.

Variability of grammars is the concern of both dialectology and typology. Therefore, the focus here is on the typologically relevant issue of what phonological features characterize each group of dialects. The study is based on evidence drawn from comparing two aspects of Berber dialects of the south and of the north-namely, syllable structure and spirantisation. From these facts, specific requirements for an architecture of grammar follow: a grammar must allow for variable outputs and preference directions. How these requirements can be satisfied within an Optimality-theoretic framework is the subject of the present paper.