Victor Braberman

Rodrigo Castaño, Victor Braberman, Diego Garbervetsky et al.

Software Model Checkers have shown outstanding performance improvements in recent times. Moreover, for specific use cases, formal verification techniques have shown to be highly effective, leading to a number of high-profile success stories. However, widespread adoption remains unlikely in the short term and one of the remaining obstacles in that direction is the vast number of instances which software model checkers cannot fully analyze within reasonable memory and CPU bounds. The majority of verification tools fail to provide a measure of progress or any intermediate verification result when such situations occur. Inspired in the success that coverage metrics have achieved in industry, we propose to adapt the definition of coverage to the context of verification. We discuss some of the challenges in pinning down a definition that resembles the deeply rooted semantics of test coverage. Subsequently we propose a definition for a broad family of verification techniques: those based on Abstract Reachability Trees. Moreover, we discuss a general approach to computing an under-approximation of such metric and a specific heuristic to improve the performance. Finally, we conduct an empirical evaluation to assess the viability of our approach.

Rodrigo Castaño, Victor Braberman, Diego Garbervetsky et al.

Software model checking constitutes an undecidable problem and, as such, even an ideal tool will in some cases fail to give a conclusive answer. In practice, software model checkers fail often and usually do not provide any information on what was effectively checked. The purpose of this work is to provide a conceptual framing to extend software model checkers in a way that allows users to access information about incomplete checks. We characterize the information that model checkers themselves can provide, in terms of analyzed traces, i.e. sequences of statements, and safe cones, and present the notion of execution reports, which we also formalize. We instantiate these concepts for a family of techniques based on Abstract Reachability Trees and implement the approach using the software model checker CPAchecker. We evaluate our approach empirically and provide examples to illustrate the execution reports produced and the information that can be extracted.

Daniel Ciolek, Victor Braberman, Nicolás D'Ippolito et al.

This paper presents a Directed Controller Synthesis (DCS) technique for discrete event systems. The DCS method explores the solution space for reactive controllers guided by a domain-independent heuristic. The heuristic is derived from an efficient abstraction of the environment based on the componentized way in which complex environments are described. Then by building the composition of the components on-the-fly DCS obtains a solution by exploring a reduced portion of the state space. This work focuses on untimed discrete event systems with safety and co-safety (i.e. reachability) goals. An evaluation for the technique is presented comparing it to other well-known approaches to controller synthesis (based on symbolic representation and compositional analyses).

Victor Braberman, Nicolas D'Ippolito, Jeff Kramer et al.

An architectural approach to self-adaptive systems involves runtime change of system configuration (i.e., the system's components, their bindings and operational parameters) and behaviour update (i.e., component orchestration). Thus, dynamic reconfiguration and discrete event control theory are at the heart of architectural adaptation. Although controlling configuration and behaviour at runtime has been discussed and applied to architectural adaptation, architectures for self-adaptive systems often compound these two aspects reducing the potential for adaptability. In this paper we propose a reference architecture that allows for coordinated yet transparent and independent adaptation of system configuration and behaviour.