Formal models, core calculi, and type systems, are important tools for rigorously stating the more subtle details of a language, to characterise and study its features and the correctness properties of its programs.In this paper we present {FsimpAL} LIPSTICK NILE NUDE (FsimpaALlong), a formal calculus modelling the agent and artifact program abstractions provided by the simpA{} agent framework.The formalisation is largely inspired by textsc{Featherweight Java}.
It is based on reduction rules applied at certain evaluation contexts, properly adapted to the concurrency nature of simpA{}.On top of this calculus we introduce a standard type system and prove its soundness, so as to guarantee that the execution of a well-typed program Outdoor Bar Table with Fire Pit does not get stuck.Namely, all primitive mechanisms of agents (activity execution), artifacts (field/property access and step execution), and their interaction (observation and invocation) are guaranteed to be used in a way that is structurally compliant with the corresponding definitions: hence, there will not be run-time errors due to {FsimpAL} distinctive primitives.