We give a comprehensive and unifying survey of the theoretical aspects of Temporal and modal logic.

State-space exploration techniques are increasingly being used for debugging and proving correct finite-state concurrent reactive systems. The reason for this success is mainly the simplicity of these techniques. Indeed, they are easy to understand, easy to implement and, last but not least, easy to use: they are fully automatic. Moreover, the range of properties that they can verify has been substantially broadened thanks to the development of model-checking methods for various temporal logics. The main limit of state-space exploration verification techniques is the often excessive size of the state space due, among other causes, to the modeling of concurrency by interleaving. However, exploring all interleavings of concurrent events is not a priori necessary for verification: interleavings corresponding to the same concurrent execution contain related information. One can thus hope to be able to verify properties of a concurrent system without exploring all interleavings of its concu...

Translating linear temporal logic formulas to automata has proven to be an effective approach for implementing linear-time model-checking, and for obtaining many extensions and improvements to this verification method. On the other hand, for branching temporal logic, automata-theoretic techniques have long been thought to introduce an exponential penalty, making them essentially useless for model-checking. Recently, Bernholtz and Grumberg have shown that this exponential penalty can be avoided, though they did not match the linear complexity of non-automata-theoretic algorithms. In this paper we show that alternating tree automata are the key to a comprehensive automata-theoretic framework for branching temporal logics. Not only, as was shown by Muller et al., can they be used to obtain optimal decision procedures, but, as we show here, they also make it possible to derive optimal model-checking algorithms. Moreover, the simple combinatorial structure that emerges from the a...

We investigate extensions of temporal logic by connectives defined by finite automata on infinite words. We consider three different logics, corresponding to three different types of acceptance conditions (finite, looping and repeating) for the automata. It turns out, however, that these logics all have the same expressive power and that their decision problems are all PSPACE-complete. We also investigate connectives defined by alternating automata and show that they do not increase the expressive power of the logic or the complexity of the decision problem. 1 Introduction For many years, logics of programs have been tools for reasoning about the input/output behavior of programs. When dealing with concurrent or nonterminating processes (like operating systems) there is, however, a need to reason about infinite computations. Thus, instead of considering the first and last states of finite computations, we need to consider the infinite sequences of states that the program goes through...

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Temporal logic is obtained by adding temporal connectives to a logic language. Explicit references to time are hidden inside the temporal connectives. Different variants of temporal logic use different sets of such connectives. In this chapter, we survey the fundamental varieties of temporal logic and describe their applications in information systems. Several features of temporal logic make it especially attractive as a query and integrity constraint language for temporal databases. First, because the references to time are hidden, queries and integrity constraints are formulated in an abstract, representationindependent way. Second, temporal logic is amenable to efficient implementation. Temporal logic queries can be translated to an algebraic language. Temporal logic constraints can be efficiently enforced using auxiliary stored information. More general languages, with explicit references to time, do not share these properties. Recent research has proposed various implementation t...

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. There is a growing need for reliable methods of designing correct reactive systems such as computer operating systems and air traffic control systems. It is widely agreed that certain formalisms such as temporal logic, when coupled with automated reasoning support, provide the most effective and reliable means of specifying and ensuring correct behavior of such systems. This paper discusses known complexity and expressiveness results for a number of such logics in common use and describes key technical tools for obtaining essentially optimal mechanical reasoning algorithms. However, the emphasis is on underlying intuitions and broad themes rather than technical intricacies. 1 Introduction There is a growing need for reliable methods of designing correct reactive systems. These systems are characterized by ongoing, typically nonterminating and highly nondeterministic behavior. Examples include operating systems, network protocols, and air traffic control systems. There is w...

We study in a first part of this paper safety and liveness properties for any given program semantics. We give a topological definition of these properties using a safety preorder. Then, we consider the case of branching time semantics where a program is modeled by a set of infinite computation trees modulo bisimulation. We propose and study a safety preorder for this semantics based on simulation and dealing with silent actions. We focus on regular safety properties and characterize them by both tree-automata and formulas of a branching time logic. We show that verifying safety properties on trees reduces to simulation testing. 1 Introduction The properties of parallel systems may be classified according to the type of behaviors they describe. Several classes of properties are distinguished such as safety, liveness, fairness, termination or recurrence properties. Such a classification allows structuring a program specification into several components; each of these components may be ...

This paper describes a generic tableau algorithm, which is the basis for a general customizable method for producing oracles from temporal logic specifications. A generic argument gives semantic rules with which to build the semantic tableau for a specification. Parameterizing the tableau algorithm by semantic rules permits it to easily accommodate a variety of temporal operators and provides a clean mechanism for fine-tuning the algorithm to produce efficient oracles. The paper develops conditions to ensure that a set of rules results in a correct tableau procedure. It gives sample rules for a variety of linear-time temporal operators and shows how rules are tailored to reduce the size of an oracle. Keywords: formal specification, verification, specificationbased test oracles, tableau methods, propositional temporal logic, test validation. 1 Introduction Temporal specifications describe constraints on the order in which events can occur in executions of a concurrent software syste...