DEVS-Ruby: a Domain Specific Language for DEVS Modeling and Simulation (WIP). This paper introduces a new Discrete EVent system Specification (DEVS) modeling and simulation library implemented in Ruby. Its syntactic sugar and features such as monkey patching, lexical closures, custom dispatch behavior and native plug-in API provides strong support to grow a Domain Specific Language (DSL). The library, by providing an internal DSL, allows formal specifications of DEVS models. The greatest strength of DEVS-Ruby lies in the extensibility of the DSL, allowing to meet each modeler’s domain specific vocabulary and thus, to evolve from a general modeling and simulation formalism to a specialized tool.