<b>CSim</b> ^<i>2</i>

To make feasible and scalable the verification of large complex concurrent systems, it is necessary use compositional techniques even at highest abstraction layers. When focusing on lowest software layers, such as implementation or machine code, high level detail those layers makes direct properties very difficult expensive. It therefore essential to allowing simplify these One technique tackle this challenge top-down where by means simulation verified top (representing abstract specifications a system) are propagated down (that an layers). There no need say that systems implies greater complexity, having check between also desirable when seeking for both feasibility scalability refinement verification. In article, we present CSim 2 (compositional) rely-guarantee-based framework in Isabelle/HOL theorem prover. uses CSimpl, language with degree expressiveness designed specification programs. Thanks its expressibility, CSimpl able model many features found real world programming languages like exceptions, assertions, procedures. provides rely-guarantee compositionally reason specifications. Focusing verification, simulation-based preservation from implementations. By using framework, proven (abstract specifications) (source code) each component system. Finally, show usability running case study over two Arinc-653 communication service. study, prove property specification, preserve lower