One of the main problems of the UML is the inaccuracy to represent the concept of context, in addition to being rigid to incorporate new models. The same way, the current modeling tools do not support the validation and representation of context concepts. In this scenario, the paper proposes an extension of UML for modeling context, which aims not only to allow the representation and validation of the main aspects of context, but also develop a domain-specific modeling environment. Thus, it is expected to enable a more appropriate support for the context modeling, assisting in the development of context-aware systems.