Distributed event-based systems have risen in significance over the last few years across many different application domains. Still, the configuration of available communication middleware solutions remains an elaborate task driven by technical terms and manual performance optimization. We present the M2etis Quality-of-service-aware Semantics Modeling Language (MATINEE), a domain-specific language for modeling the QoS requirements and semantic properties of event-based systems in the terminology of the application domain. No knowledge of the technical terms of the underlying middleware solution is required by the application developers to conduct the configuration. Embedded in a novel configuration methodology provided by the M2etis project, MATINEE specifications are interpreted to automatically derive optimal middleware configurations without the need for manual optimization. The purpose of MATINEE is to provide a flexible language that can easily be adapted to different application domains. We focus on the language specification of MATINEE, briefly sketch our configuration methodology and present related language approaches.