On model checking data-independent systems with arrays without reset

A system is data-independent with respect to a data type X iff the operations it can perform on values of type X are restricted to just equality testing. The system may also store, input and output values of type X. We study model checking of systems which are data-independent with respect to two distinct type variables X and Y, and may in addition use arrays with indices from X and values from Y . Our main interest is the following parameterised model-checking problem: whether a given program satisfies a given temporal-logic formula for all non-empty nite instances of X and Y . Initially, we consider instead the abstraction where X and Y are infinite and where partial functions with finite domains are used to model arrays. Using a translation to data-independent systems without arrays, we show that the u-calculus model-checking problem is decidable for these systems. From this result, we can deduce properties of all systems with finite instances of X and Y . We show that there is a procedure for the above parameterised model-checking problem of the universal fragment of the u-calculus, such that it always terminates but may give false negatives. We also deduce that the parameterised model-checking problem of the universal disjunction-free fragment of the u-calculus is decidable. Practical motivations for model checking data-independent systems with arrays include verification of memory and cache systems, where X is the type of memory addresses, and Y the type of storable values. As an example we verify a fault-tolerant memory interface over a set of unreliable memories.Comment: Appeared in Theory and Practice of Logic Programming, vol. 4, no. 5&6, 200

Well-Founded Semantics for Extended Datalog and Ontological Reasoning

The Datalog± family of expressive extensions of Datalog has recently been introduced as a new paradigm for query answering over ontologies, which captures and extends several common description logics. It extends plain Datalog by features such as existentially quantified rule heads and, at the same time, restricts the rule syntax so as to achieve decidability and tractability. In this paper, we continue the research on Datalog±. More precisely, we generalize the well-founded semantics (WFS), as the standard semantics for nonmonotonic normal programs in the database context, to Datalog± programs with negation under the unique name assumption (UNA). We prove that for guarded Datalog± with negation under the standard WFS, answering normal Boolean conjunctive queries is decidable, and we provide precise complexity results for this problem, namely, in particular, completeness for PTIME (resp., 2-EXPTIME) in the data (resp., combined) complexity

Runtime verification for biochemical programs

The biochemical paradigm is well-suited for modelling autonomous systems and new programming languages are emerging from this approach. However, in order to validate such programs, we need to define precisely their semantics and to provide verification techniques. In this paper, we consider a higher-order biochemical calculus that models the structure of system states and its dynamics thanks to rewriting abstractions, namely rules and strategies. We extend this calculus with a runtime verification technique in order to perform automatic discovery of property satisfaction failure. The property specification language is a subclass of LTL safety and liveness properties