This article presents Kuaba, a new design rationale representation approach that enables employing design rationale to support reuse of model-based designs, particularly, software design. It is shown that this can be achieved through the adoption of an appropriate vocabulary that allows design rationale representations to be computationally processed. The architecture and implementation of an integrated design environment to support recording design rationale using Kuaba is also shown. The Kuaba approach integrates the design rationale representation model with the formal semantics provided by the metamodel of the design method or modeling language used for describing the artifact being designed. This integration makes the design rationale representations more specific according to the design methods and enables a type of software design reuse at the highest abstraction level, where rationales can be integrated and reemployed in designing a new artifact.