This paper deals with the problem of expression and representation of robotics software architectures, at a level of abstraction high enough, and independent of the implementation platform, taking into account real-time properties. It also addresses the problem of standard representation, communication between domain experts, and therefore that of reusability of these architectures. It presents RsaML (Robotic Software Architecture Modeling Language), a Domain Specific Modeling Language (DSML) for robotics software architectures that we proposed in order to solve the problems mentioned above. The conceptual model defining the terminology, and the hierarchy of concepts used for the description and representation of robotic architectures in RsaML are presented in this paper. RsaML is defined through a meta-model which represents the abstract syntax of the language. Real-time properties of robotics software architectures are identified and included in the meta model. The use of RsaML is illustrated through the definition of a robotic system and the description of its architecture with the help of the language. The support tool used for this work is the Eclipse Modeling Framework (EMF).