Domain Specific Modeling (DSM) has gained a lot of research attention, especially concerning costs/time optimization and code quality aspects. On the other hand, CAC (Context Aware Computing) has recently emerged as a new computing paradigm promising adaptable systems development. DSM approach for Context aware service oriented systems (SOS) raises many challenges. Particularly, the challenge of engineering such systems, which consists of the definition of modeling approaches, processes, techniques and tools to facilitate construction of these systems. In this paper, we propose a DSM approach for adaptable service oriented systems named CADSSO (Context Aware, Domain Specific and Service Oriented) modeling approach. Our modeling approach is based on five models: domain specific services model (conforms to a domain specific services meta model) which is a representation of the domain specific services; service variability model (conforms to our service variability meta-model), it formulates services forms of adaptation; domain specific context model (conforms to our context meta-model), symbolize the services context of use; adaptation rules model, which is the joint between service variability model and context model; and domain specific business rules model, used to model domain specific business.