Refined Interfaces for Compositional Verification

The compositional verification approach of Graf & Steffen aims at avoiding state space explosion for individual processes of a concurrent system. It relies on interfaces that express the behavioural constraints imposed on each process by synchronization with the other processes, thus preventing the exploration of states and transitions that would not be reachable in the global state space. Krimm & Mounier, and Cheung & Kramer proposed two techniques to generate such interfaces automatically. In this report, we propose a refined interface generation technique that derives the interface of a process automatically from the examination of (a subset of) concurrent processes. This technique is applicable to formalisms where concurrent processes are composed either using synchronization vectors or process algebra parallel composition operators (including those of CCS, CSP, muCRL, LOTOS, and E-LOTOS). We implemented this approach in the EXP.OPEN 2.0 tool of the CADP toolbox. Several experiments indicate state space reductions by more than two orders of magnitude for the largest processes

Compositional Verification using CADP of the ScalAgent Deployment Protocol for Software Components

In this report, we present the application of the Cadp verification toolbox to check the correctness of an industrial protocol for deploying and configuring transparently a large set of heterogeneous software components over a set of distributed computers/devices. To cope with the intrinsic complexity of this protocol, compositional verification techniques have been used, including incremental minimization and projections over automatically generated interfaces as advocated by Graf & Steffen and Krimm & Mounier. Starting from the Xml description of a configuration of components to be deployed by the protocol, a translator produces a set of Lotos descriptions, µ-calculus formulas, and the corresponding compositional verification scenario to be executed. The approach is fully automated, as formal methods and tool invocations are made invisible to the end-user, who only has to check the verification results for the configuration under study. Due to the use of compositional verification, the approach can scale to large configurations. So far, Lotos descriptions of more than seventy concurrent processes have been verified successfully

Study of adenovirus packaging

Adenovirus (AdV) assembly is a multistep process that begins with the accumulation of viral structural proteins and DNA in the nucleus of the infected cell. After empty or precursor capsids are assembled from these structural proteins, the recognition and packaging of the viral genome into the empty capsids follows. Specific recognition of viral genome is dependent on the presence of a packaging domain located between 220 and 400 nucleotides from the left end of the genome. The human Ad serotype 5 (HAdV5) packaging domain consists of seven A repeats, designated as A1 to A7. The IVa2 protein is the first factor to bind at the A repeats thus making it essential for genome recognition. Apart from recognition, IVa2 is essential for genome packaging since IVa2 deletion mutants fail to package the genome. IVa2 is also thought to be the DNA packaging ATPase. Despite these identified facts, the complete mechanistic details of AdV assembly and packaging are not known. Attempting to discover other novel proteins involved in AdV assembly and packaging, we found that the viral proteins L4 33K and DNA binding protein (DBP) interact with IVa2. The IVa2, L4 33K and DBP proteins form a complex in virus-infected cells, co-localize even in the absence of other viral proteins, and are located at single sites on viral particles, implying that IVa2, 33K and DBP are possibly co-localized at a unique vertex and together participate in genome packaging. IVa2 and DBP are present in both empty and mature capsids, whereas 33K is present only in empty capsids. As anticipated for proteins involved in genome packaging, the purified IVa2 and 33K formed ring-like oligomers and their oligomers were also detected in purified virus. Using recombinant proteins expressed and purified from soluble fraction of E. coli, ATPase activity of IVa2 was demonstrated in the presence of 33K and the viral genome in an in vitro assay. These results provide compelling evidence for role of 33K as small terminase equivalent for AdV assembly

Exp.Open 2.0: A Flexible Tool Integrating Partial Order, Compositional, and On-the-fly Verification Methods

It is desirable to integrate formal verification techniques applicable to different languages. We present Exp.Open 2.0, a new tool of the Cadp verification toolbox which combines several features. First, Exp.Open 2.0 allows to describe concurrent systems as a composition of finite state machines, using either synchronization vectors, or parallel composition, hiding, renaming, and cut operators from several process algebras (Ccs, Csp, Lotos, E-Lotos, µCrl). Second, together with other tools of Cadp, Exp.Open 2.0 allows state space generation and on-the-fly exploration. Third, Exp.Open 2.0 implements on-the-fly partial order reductions to avoid the generation of irrelevant interleavings of independent transitions. Fourth, Exp.Open 2.0 allows to export models towards other tools using interchange formats such as automata networks and Petri nets. Finally, we show some practical applications and measure the efficiency of Exp.Open 2.0 on several benchmarks