The Software-as-a-Service delivery model bears new challenges for application developers. Especially in the context of enterprise resource planning software targeting the SME market, new problems arise. Most of them agglomerate around the occurrence of multi-tenancy. This paper describes the framework MapperMania which aims to establish an abstraction layer between the persistence layer and the domain model. Leveraging MapperMania, the domain model is able to abstract from multi-tenancy and changes in the underlying infrastructure.