Language processors can be derived from logic grammars. That several concerns in the processor such as parsing, several kinds of analysis or transformations, can be specified as aspects of the logic grammar is demonstred. For that purpose, the authors bring the concepts of aspect-oriented programming to Prolog in a systematic way, based on established Prolog technology. The authors illustrate that typical Prolog programming techniques can be described as generic aspects and provided in a library to support reusable concerns. A domain-specific language (DSL) is developed to improve readability of aspect-oriented specifications.