In this paper, we introduce a proposal towards a formal grammatical model that captures different types of negation uniformly, in terms of pragmatic structuring. The central objective of the paper is the analysis of the relation between focusing and negation, modeling both 'focus negation' and 'sentential negation'. We propose a modular grammatical model, with separate but interrelated representations for syntax, semantics and information structure. We argue for a two-level analysis of negation, such that next to semantics it operates at the level of information structure. The main concern of the paper is the formal grammatical modeling of the IS-level, where negation targets the communicative function determined by the given focus structure.