Specifying Weak Constraints in Processable English

Processable English (PENG) is a controlled natural language designed to specify and conceptualize knowledge in a human-readable and machine-processable way. PENG specifications can be translated unambiguously into executable answer set programs (ASP). In this paper we suggest an extension of the language PENGASP so that weak constraints can be expressed in controlled natural language and processed as part of an ASP program. In contrast to strong constraints that have always to be satisfied and are already part of the controlled natural language, we introduce weak constraints that can be weighted and prioritised and should be satisfied whenever possible. The addition of weak constraints to the controlled natural language PENGASP makes it possible to specify optimisation problems in a natural way.