This paper is about a special version of PDL, proposed by Marcus Kracht, for reasoning about sibling ordered trees. It has four basic programs corresponding to the child, parent, left- and right-sibling relations in such trees. The original motivation for this language is rooted in the field of model-theoretic syntax. Motivated by recent developments in the area of semi-structured data, and, especially, in the field of query languages for XML (eXtensible Markup Language) documents, we revisit the language. This renewed interest (...) comes with a special focus on complexity and expressivity aspects of the language, aspects that have so far largely been ignored. We survey and derive complexity results, and spend most of the paper on the most important open question concerning the language: what is its expressive power? We approach this question from two angles: Which first-order properties can be expressed? And which second-order properties? While we are still some way from definitive answers to these questions, we discuss two first-order fragments of the PDL language for ordered trees, and show how the language can be used to express some typical (second-order) problems, like the boolean circuit and the frontier problem. (shrink)

Linear temporal logic is a widely used method for verification of model checking and expressing the system specifications. The relationship between theory of automata and logic had a great influence in the computer science. Investigation of the relationship between quantum finite automata and linear temporal logic is a natural goal. In this paper, we present a construction of quantum finite automata on finite words from linear-time temporal logic formulas. Further, the relation between quantum finite automata and linear temporal logic is (...) explored in terms of language recognition and acceptance probability. We have shown that the class of languages accepted by quantum finite automata are definable in linear temporal logic, except for measure-once one-way quantum finite automata. (shrink)

We investigate the major mathematical theories of space from a modal standpoint: topology, affine geometry, metric geometry, and vector algebra. This allows us to see new fine-structure in spatial patterns which suggests analogies across these mathematical theories in terms of modal, temporal, and conditional logics. Throughout the modal walk through space, expressive power is analyzed in terms of language design, bisimulations, and correspondence phenomena. The result is both unification across the areas visited, and the uncovering of interesting new questions.

In this paper, we study the introduction of modal past temporal operators in Temporal Equilibrium Logic, an hybrid formalism that mixes linear-time modalities and logic programs interpreted under stable models and their characterisation in terms of Equilibrium Logic. We show that Kamp’s translation can also be used to translate the new extension of TEL with past operators into Quantified Equilibrium Logic. Additionally, we provide a method for removing past operators that consists in replacing past-time subformulas by fresh auxiliary atoms, obtaining (...) an equivalent formula, modulo the original alphabet. (shrink)

ABSTRACT We characterize those binary ramified frames for which propositional modal logic is as expressive as the corresponding first-order logic.

The questions od determinism, causality, and freedom have been the main philosophical problems debated since the beginning of temporal logic. The issue of the logical value of sentences about the future was stated by Aristotle in the famous tomorrow sea-battle passage. The question has inspired Łukasiewicz’s idea of many-valued logics and was a motive of A. N. Prior’s considerations about the logic of tenses. In the scheme of temporal logic there are different solutions to the problem. In the paper we (...) consider indeterministic temporal logic based on the idea of temporal worlds and the relation of accessibility between them. (shrink)

ABSTRACT Many temporal and modal logic languages can be regarded as subsets of first order logic, i.e. the semantics of a temporal logic formula is given as a first order condition on points of the underlying models (Kripke structures). Often the set of possible models is restricted to models which are trees. A temporal logic language is (first order) expressively complete, if for every first order condition for a node of a tree there exists an equivalent temporal formula which expresses (...) the same condition. In this paper expressive completeness of the temporal logic language with the set of operators U (until), S (since), and X k (k-next) is proved, and the result is extended to various other tree-like structures. (shrink)

A conjecture of Gabbay (1981) states that any class of flows of time having the property known as finite H-dimension admits a finite set of expressively complete one-dimensional temporal connectives. Here we show that the class of 'circular' structures refutes the generalisation of this conjecture to Kripke frames. We then construct from this class, by a general method, a new class of irreflexive transitive flows of time that refutes the original conjecture. Our paper includes full descriptions of a method for (...) establishing finite H-dimension for a class of structures and of the technique for extending finite H-dimension to other classes, and an introduction surveying the area of expressive completeness. (shrink)

This article surveys some of the key issues that arise when one tries to use tense logic as a metaphysical theory of the nature of time. Topics discussed include basic tense logic, tense logic and verb tense, the structure of the time series, instants of time, quantified tense logic, and the expressive resources of tense logic.

Linguistic phenomena of tense and aspect have been investigated in a great deal of theoretical work in linguistics, philosophy and computer science. Modern tense logics, established by Prior, are part of this effort. Point tense logics offer an intuitive representation of tense but lack the expressiveness to represent many aspectual structures. Interval tense logics offer more expressiveness but in the general case can be computationally intractable. From a linguistic perspective there is the problem of precisely how to formalise the aspectual (...) structures, such as a culmination and a culminated process. In this paper we define a computationally tractable augmented fragment of Halpern and Shoham's interval tense logic HS and apply it to represent a core set of aspectual structures, which are incorporated into a temporal semantics of a simple fragment of English. We model the logic fragment using timelines and define two procedures, one for constructing the minimal timelines that satisfy a formula and one for checking semantic entailments between one formula and another by comparing their timelines. The former is applied to compute models of temporal readings and the latter to check entailments between them. Possible extensions to the logic fragment and timeline models are discussed as ways of accounting for a wider range of linguistic behaviour. (shrink)

We study the notion of H-dimension and the formally stronger k-variable property, as considered by Gabbay, Immerman and Kozen. We exhibit a class of flows of time that has H-dimension 3, and admits a finite expressively complete set of onedimensional temporal connectives, but does not have the k-variable property for any finite k.

We show that the loosely guarded and packed fragments of first-order logic have the finite model property. We use a construction of Herwig and Hrushovski. We point out some consequences in temporal predicate logic and algebraic logic.

Like modal logic, temporal logic, and description logic, separation logic has become a popular class of logical formalisms in computer science, conceived as assertion languages for Hoare-style proof systems with the goal to perform automatic program analysis. In a broad sense, separation logic is often understood as a programming language, an assertion language and a family of rules involving Hoare triples. In this survey, we present similarities between separation logic as an assertion language and modal and temporal logics. Moreover, we (...) propose a selection of landmark results about decidability, complexity and expressive power. (shrink)

We present an overview of linear-time temporal logics with Presburger constraints whose models are sequences of tuples of integers. Such formal specification languages are well-designed to specify and verify systems that can be modelled with counter systems. The paper recalls the general framework of LTL over concrete domains and presents the main decidability and complexity results related to fragments of Presburger LTL. Related formalisms are also briefly presented.