Constraint LTL over clocks is a variant of CLTL, an extension of lineartime temporal logic allowing atomic assertions in a concrete constraint system. Satisfiability of CLTL over clocks is here shown to be decidable by means of a reduction to a decidable SMT (Satisfiability Modulo Theories) problem. The result is a complete Bounded Satisfiability Checking procedure, which has been implemented by using standard SMT solvers. The importance of this technique derives from the possibility of translating various continuous-time metric temporal logics, such as MITL and QTL, into CLTL over clocks itself. Although standard decision procedures of these logics do exist, they have never been realized in practice. Suitable translations into CLTL over clocks have instead allowed us the development of the first prototype tool for deciding MITL and QTL. The paper also reports preliminary, but encouraging, experiments on some significant examples of MITL and QTL formulae.

Constraint LTL over clocks is a variant of CLTL, an extension of lineartime temporal logic allowing atomic assertions in a concrete constraint system. Satisfiability of CLTL over clocks is here shown to be decidable by means of a reduction to a decidable SMT (Satisfiability Modulo Theories) problem. The result is a complete Bounded Satisfiability Checking procedure, which has been implemented by using standard SMT solvers. The importance of this technique derives from the possibility of translating various continuous-time metric temporal logics, such as MITL and QTL, into CLTL over clocks itself. Although standard decision procedures of these logics do exist, they have never been realized in practice. Suitable translations into CLTL over clocks have instead allowed us the development of the first prototype tool for deciding MITL and QTL. The paper also reports preliminary, but encouraging, experiments on some significant examples of MITL and QTL formulae.

This paper introduces a novel technique to decide the satisfiability of formulae written in the language of Linear Temporal Logic with both future and past operators and atomic formulae belonging to constraint system D (CLTLB(D) for short). The technique is based on the concept of bounded satisfiability, and hinges on an encoding of CLTLB(D) formulae into QF-EUD, the theory of quantifierfree equality and uninterpreted functions combined with D. Similarly to standard LTL, where bounded model-checking and SAT-solvers can be used as an alternative to automata-theoretic approaches to model-checking, our approach allows users to solve the satisfiability problem for CLTLB(D) formulae through SMT-solving techniques, rather than by checking the emptiness of the language of a suitable automaton. The technique is effective, and it has been implemented in our Zot formal verification tool.

This paper defines CLTLB(D), an extension of PLTLB (PLTL with both past and future operators) augmented with atomic formulae built over a constraint system D. The paper introduces suitable restrictions and assumptions that make the satisfiability problem decidable in many cases, although the problem is undecidable in the general case. Decidability is shown for a large class of constraint systems, and an encoding into Boolean logic is defined. This paves the way for applying existing SMT-solvers for checking the Bounded Reachability problem, as shown by various experimental results

Cloud-based elastic systems run on a cloud infrastructure and have the capability of dynamically adjusting the allocation of their resources in response to changes in the workload, in a way that balances the trade-off between the desired quality-of-service and the operational costs. The actual elastic behavior of these systems is determined by a combination of factors, including the input workload, the logic of the elastic controller determining the type of resource adjustment, and the underlying technological platform implementing the cloud infrastructure. All these factors have to be taken into account to express the desired elastic behavior of a system, as well as to verify whether the system manifests or not such a behavior.In this paper, we take a first step into these directions, by proposing a formalization, based on the CLTL t (D) temporal logic, of several concepts and properties related to the behavior of cloud-based elastic systems. We also report on our preliminary evaluation of the feasibility to check the (formalized) properties on execution traces using an automated verification tool.

We present a model-driven approach for the creation of formally verified scenarios involving human-robot interaction in healthcare settings. The work offers an innovative take on the application of formal methods to human modeling, as it incorporates physiology-related aspects. The model, based on the formalism of Hybrid Automata, includes a stochastic component to capture the variability of human behavior, which makes it suitable for Statistical Model Checking. The toolchain is meant to be accessible to a wide range of professional figures. Therefore, we have laid out a user-friendly representation format for the scenario, from which the full formal model is automatically generated and verified through the Uppaal tool. The outcome is an estimation of the probability of success of the mission, based on which the user can refine the model if the result is not satisfactory.

Abstract:We describe a business workflow case study with abnormal behavior management (i.e. recovery) and demonstrate how temporal logics and model checking can provide a methodology to iteratively revise the design and obtain a correct-by construction system. To do so we define a formal semantics by giving a compilation of generic workflow patterns into LTL and we use the bound model checker Zot to prove specific properties and requirements validity. The working assumption is that such a lightweight approach would easily fit into processes that are already in place without the need for a radical change of procedures, tools and people's attitudes. The complexity of formalisms and invasiveness of methods have been demonstrated to be one of the major drawback and obstacle for deployment of formal engineering techniques into mundane projects.

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