Quality Domain Specific Language (QDSL) is a model-driven approach providing a taxonomy, model, and visual editing tool for evaluating and benchmarking the quality of composite applications in cloud environments. Our language and associated modeling tool provide visual and textual means for constructing mathematical algorithms needed for computing aggregated quality assessment of cloud services. QDSL enables the illustration and definition of metrics, measurements and indicators, relationships for computation, and transformation functions that normalize the measurements into relative quality scoring. As a result, QDSL provides a structure that guides overall quality assessments. The computation algorithm is structured in a visual manner and associates the quality assessments graph with the structure of the cloud composite application in a hybrid environment. QDSL supports transformation from physical measurements into scoring comparative assessments of benchmarked provided IT solutions. This paper presents a basic model for QDSL and examples of usage. A prototypical eclipse EMF modeling tool of QDSL is used for communication, whereas commercial monitoring tools implement the instantiated models for evaluating service qualities.