We introduce and evaluate dynamic branching strategies for solving Qualitative Constraint Networks (QCNs), which are networks that are mostly used to represent and reason about spatial and temporal information via the use of simple qualitative relations, e.g., a constraint can be “Task A is scheduled after or during Task C”. In qualitative constraint-based reasoning, the state-of-the-art approach for

Spiking neural P systems with inhibitory rules (in short, IR-SN P systems) are a kind of bio-inspired computing systems, which are abstracted by the inhibitory synaptic mechanism of biological neurons. IR-SN P systems work in synchronous mode. This paper investigates their sequential version, sequential IR-SN P systems (in short, IR-SSN P systems). In sequential mode, not only the rules in each neuron

Given a collection of multisets {X1,X2,…,Xk} (k≥2) of positive integers, a multiset S is a common integer partition for them if S is an integer partition of every multiset Xi,1≤i≤k. The minimum common integer partition (k-MCIP) problem is defined as to find a CIP for {X1,X2,…,Xk} with the minimum cardinality. We present a 65-approximation algorithm for the 2-MCIP problem, improving the previous best

We introduce the notion of a deterministic biautomaton, a device that reads inputs from both ends, and admits at most one computation on every input word. We show that deterministic biautomata recognize a class of languages which is properly included in the class of all linear languages, and which is not comparable to the class of languages recognized by deterministic one-turn pushdown automata. We

We study reachability problems for various nondeterministic polynomial maps in Zn. We prove that the reachability problem for very simple three-dimensional affine maps (with independent variables) is undecidable and is PSPACE-hard for both two-dimensional affine maps and one-dimensional quadratic maps. Then we show that the complexity of the reachability problem for maps without functions of the form

The Caucal hierarchy contains graphs that can be obtained from finite directed graphs by alternately applying the unfolding operation and inverse rational mappings. The goal of this work is to check whether the hierarchy is closed under interpretations in logics extending the monadic second-order logic by the unbounding quantifier, U (saying that a subformula holds for arbitrarily large finite sets)

In a typical regex crossword puzzle, one is given two non-empty lists 〈R1,…,Rm〉 and 〈C1,…,Cn〉 of regular expressions (regexes) over some alphabet, and the challenge is to fill in an m×n grid of characters such that the string formed by the ith row is in L(Ri) and the string formed by the jth column is in L(Cj), for all 1≤i≤m and 1≤j≤n. We consider a restriction of this puzzle where all the Ri are equal

A Conditional Simple Temporal Network with Uncertainty and Decisions (CSTNUD) is a formalism for temporal plans that models controllable and uncontrollable durations as well as controllable and uncontrollable choices simultaneously. In the classic top-down model-based engineering approach, a designer builds CSTNUDs to model, validate and execute some temporal plans of interest. In this paper, we investigate

The state complexity of a finite(-state) automaton intuitively measures the size of the description of the automaton. Sakoda and Sipser [STOC 1972, pp. 275–286] were concerned with nonuniform families of finite automata and they discussed the behaviors of the nonuniform complexity classes defined by such families of finite automata having polynomial-size state complexity. In a similar fashion, we introduce

We study the complexity of regular matching and inclusion for compressed tree patterns with context variables subject to regular constraints. Context variables with regular constraints permit to properly generalize on unranked tree patterns with hedge variables. Regular inclusion on unranked tree patterns is relevant to certain query answering on Xml streams with references. We show that regular matching

Fusion grammars are a novel approach to the generation of hypergraph languages. Context-dependent fusion grammars extend them in such a way that the application of fusion rules can be restricted by positive and negative context conditions. In this paper, we show that several variants of Petri nets can be transformed into these grammars such that the reachable markings are in one-to-one correspondence

We develop a general framework for weighted parsing which is built on top of grammar-based language models and employs multioperator monoids (M-monoids) as weight algebras. It generalizes previous work in that area, e.g., semiring parsing and weighted deductive parsing, and also covers applications outside the classical scope of parsing, e.g., algebraic dynamic programming. More specifically, we introduce

A k-antipower (for k≥2) is a concatenation of k pairwise distinct words of the same length. The study of fragments of a word being antipowers was initiated by Fici et al. (ICALP 2016) and first algorithms for computing such fragments were presented by Badkobeh et al. (Inf. Process. Lett., 2018). We address two open problems posed by Badkobeh et al. We propose efficient algorithms for counting and reporting

We investigate the maximum number of distinct palindromic sub-words in a two-dimensional finite word. We give tight bounds for the maximum number of distinct palindromic sub-words in two-row periodic/aperiodic words. Using this, we give upper bounds for the number of distinct palindromic sub-words for 2D words of larger sizes. Lastly, we propose a better bound for any finite 2D word.

This paper approaches, using structural complexity theory, the question of whether there is a chasm between knowing an object exists and getting one's hands on the object or its properties. In particular, we study the nontransparency of so-called backbones. A backbone of a boolean formula F is a collection S of its variables for which there is a unique partial assignment aS such that F[aS] is satisfiable

In this paper we revisit the PAC learnability of the class of intersections of polynomially many halfspaces over boolean cubes in the membership query model. The previous works (Klivans and Sherstov 2009, Angluin and Kharitonov 1995) imply the unlearnability of the class in this model based on some cryptographic assumptions. More precisely, the result is achieved by establishing the unlearnability

Stable event structures, and their duality with prime algebraic domains, represent a landmark of concurrency theory, since they provide a neat characterisation of causality in computations. As such, they have been used for defining the concurrent semantics of many formalisms, from Petri nets to (linear) graph rewriting systems. Stability however is restrictive for formalisms with “fusion”, where a

Two types of cells for bio-inspired computations are neurons and bacteria: the former have “simple” neurons that connect together to become more useful, i.e. structure is important to their overall function; the latter have bacteria “processing” DNA such as plasmids. We combine inspirations from both cell types as neural-like P systems with plasmids or NP P systems: bacteria are nodes in a digraph

We propose a new generalisation of Cayley automatic groups, varying the time complexity of computing multiplication, and language complexity of the normal form representatives. We first consider groups which have normal form language in the class C and multiplication by generators computable in linear time on a certain restricted Turing machine model (position–faithful one–tape). We show that many

In the ad-hoc radio network model, nodes communicate with their neighbors via radio signals, without knowing the topology of the underlying digraph. We study the information gathering problem, where each node has a piece of information called a rumor, and the objective is to transmit all rumors to the designated target node. For the model without any collision detection we provide an O˜(n1.5) deterministic

Turi and Plotkin's bialgebraic semantics is an abstract approach to specifying the operational semantics of a system, by means of a distributive law between its syntax (encoded as a monad) and its dynamics (an endofunctor). This setup is instrumental in showing that a semantic specification (a coalgebra) satisfies desirable properties: in particular, that it is compositional. In this work, we use the

We consider forests as tuples of trees and introduce weighted forest automata (wfa) over M-monoids. A wfa acts on each individual tree in a forest like a weighted tree automaton over the same M-monoid. In order to combine the values of trees in forests, a wfa uses an associative multiplication operation that distributes over the addition of the M-monoid. We continue by introducing two semantics for

In this paper we study the family of freezing cellular automata (FCA) in the context of asynchronous updating schemes. A cellular automaton is called freezing if there exists an order of its states, and the transitions are only allowed to go from a lower to a higher state. A cellular automaton is asynchronous if at each time-step only one cell is updated. We define the problem AsyncUnstability, which

Tissue P systems with symport/antiport rules are non-deterministic parallel bio-inspired devices that evolve by communicating objects between two regions in both directions. In this paper, an interesting type of tissue P systems, called monodirectional tissue P systems with symport rules (MTS P systems) is considered, where communication happens between two regions only in one direction, and never

A correspondence is established between one-variable fragments of (first-order) intermediate logics defined over a fixed countable linear frame and Gödel modal logics defined over many-valued equivalence relations with values in a closed subset of the real unit interval. It is also shown that each of these logics can be interpreted in the one-variable fragment of the corresponding constant domain intermediate

In this paper we introduce a language of first-order hybrid logic in which function symbols are interpreted by partial functions and prove a number of completeness results. Syntactically, our language builds on the basic propositional hybrid language, has a primitive unary predicate symbol DEN which tests whether a term denotes or not, and permits satisfaction operators to rigidify predicate and function

We investigate language interpretations of two extensions of the Lambek calculus: with additive conjunction and disjunction and with additive conjunction and the unit constant. For extensions with additive connectives, we show that conjunction and disjunction behave differently. Adding both of them leads to incompleteness due to the distributivity law. We show that with conjunction only no issues with

We give a computational interpretation to an abstract formulation of Krull's theorem, by analysing its classical proof based on Zorn's lemma. Our approach is inspired by proof theory, and uses a form of update recursion to replace the existence of maximal ideals. Our main result allows us to derive, in a uniform way, algorithms which compute witnesses for existential theorems in countable abstract

We give Hennessy-Milner classes for intuitionistic, dual-intuitionistic and bi-intuitionistic logic interpreted in intuitionistic Kripke models, and generalise these results to modal (dual- and bi-)intuitionistic logics. Our main technical tools are image-compact and pre-image-compact relations that provide a semantical description of modal saturation properties.

This paper focuses on globally sound but possibly locally unsound analytic sequent calculi for quantifier macros defined by sequences of quantifiers. It is demonstrated that no locally sound analytic representation based on the usual eigenvariable condition exists. In consequence, representations by globally sound but possibly locally unsound analytic sequent calculi are used. Cut-elimination is shown

Turing's famous ‘machine’ framework provides an intuitively clear conception of ‘computing with real numbers’. A recursive counterexample to a theorem shows that the theorem does not hold when restricted to computable objects. These counterexamples are often crucial in establishing reversals in the Reverse Mathematics program. All the previous is essentially limited to a language that can only express

Natural language semantics has recently sought to combine the complementary strengths of formal and distributional approaches to meaning. More specifically, proposals have been put forward to augment formal semantic machinery with distributional meaning representations, thereby introducing the notion of semantic similarity into formal semantics, or to define distributional systems that aim to incorporate

Logics with team semantics provide alternative means for descriptive characterization of complexity classes. Dependence and independence logic are both known to capture non-deterministic polynomial time, and the frontiers of tractability in these logics are relatively well understood. Inclusion logic is similar to these team-based logical formalisms with the exception that it corresponds to deterministic

Beklemishev introduced an ordinal notation system for the Feferman-Schütte ordinal Γ0 based on the autonomous expansion of provability algebras. In this paper we present the logic BC (for Bracket Calculus). The language of BC extends said ordinal notation system to a strictly positive modal language. Thus, unlike other provability logics, BC is based on a self-contained signature that gives rise to

We introduce proper display calculi for basic monotonic modal logic, the conditional logic CK and a number of their axiomatic extensions. These calculi are sound, complete, conservative, and enjoy cut elimination and subformula property. Our proposal applies the multi-type methodology in the design of proper display calculi, starting from a semantic analysis which motivates syntactic translations from

An automaton is unambiguous if for every input it has at most one accepting computation. An automaton is finitely (respectively, countably) ambiguous if for every input it has at most finitely (respectively, countably) many accepting computations. An automaton is boundedly ambiguous if there is k∈N, such that for every input it has at most k accepting computations. We consider nondeterministic Büchi

The problem of matching a query string to a directed graph, whose vertices are labeled by strings, has application in different fields, from data mining to computational biology. Several variants of the problem have been considered, depending on the fact that the match is exact or approximate and, in the approximate case, which edit operations are considered and where they are allowed. In this paper

The suffix tree is a fundamental data structure in stringology, but its space usage, though linear, is an important problem in applications like Bioinformatics. We design and implement a new compressed suffix tree (CST) targeted to highly repetitive texts, such as large genomic collections of the same species. Our first contribution is to enhance the Block Tree, a data structure that captures the repetitiveness

We investigate inference of variable-length codes in other domains of computer science, such as noisy information transmission or information retrieval-storage: in such topics, traditionally mostly constant-length codewords act. The study is relied upon the two concepts of independent and closed sets: given an alphabet A and a binary relation τ⊆A⁎×A⁎, a set X⊆A⁎ is τ-independent if τ(X)∩X=∅; X is τ-closed

A real number x is absolutely normal if, for every base b≥2, every two equally long strings of digits appear with equal asymptotic frequency in the base-b expansion of x. This paper presents an explicit algorithm that generates the binary expansion of an absolutely normal number x, with the nth bit of x appearing after npolylog(n) computation steps. This speed is achieved by simultaneously computing

We investigate systems of equations and the first-order theory of one-relator monoids. We describe a family F of one-relator monoids of the form 〈A|w=1〉 where for each monoid M in F, the longstanding open problem of decidability of word equations with length constraints reduces to the Diophantine problem (i.e. decidability of systems of equations) in M. We achieve this result by finding an interpretation

Schedulability is a fundamental problem in analyzing real-time systems, but it often has to be approximated due to the intrinsic computational hardness. As the most popular polynomial-time and practical algorithm for deciding schedulability on multiprocessor platforms, the speedup factor of Partitioned-EDF is challenging to analyze and is far from being determined. Partitioned-EDF was first proposed

We study the capabilities of probabilistic finite-state machines that act as verifiers for certificates of language membership for input strings, in the regime where the verifiers are restricted to toss some fixed nonzero number of coins regardless of the input size. Say and Yakaryılmaz showed that the class of languages that could be verified by these machines within an error bound strictly less than

A k-threshold function on a rectangular grid of size m×n is the conjunction of k threshold functions on the same domain. In this paper, we focus on the case k=2 and show that the number of two-dimensional 2-threshold functions is 2512π4m4n4+o(m4n4).

In this paper we consider a generalization of the well-known budgeted maximum coverage problem. We are given a ground set of elements and a set of bins. Each bin has its own cost and the cost of each element depends on its associated bin. The goal is to find a subset of elements along with an associated set of bins such that the overall costs of both is at most a given budget, and the profit is maximized

Outsourcing computation has gained significant popularity in recent years due to the prevalence of cloud computing. There are two main security concerns in outsourcing computation: how to guarantee the cloud server performs the computation correctly and how to keep the client's data secret. The single-server verifiable computation (SSVC) of Gennaro, Gentry and Parno (Crypto'10) enables a client to

In the well-known cake cutting problem, a cake needs to be divided among n players who possibly have different valuations for different pieces of the cake. We consider a variation of this problem in which the cake represents chores that need to be allocated. As the players are assumed to be work-averse, this means that each agent now desires to get as little of the cake as possible. In this work, we

We consider the following variant of the mortality problem: given k×k matrices A1,A2,…,At, do there exist t nonnegative integers m1,m2,…,mt such that the product A1m1A2m2⋯Atmt is equal to the zero matrix? It is known that this problem is decidable when t≤2 for matrices over algebraic numbers but becomes undecidable for sufficiently large t and k, even for integral matrices. In this paper, we prove

Given a set P of points in the Euclidean plane and two triangulations of P, the flip distance between these two triangulations is the minimum number of flips required to transform one triangulation into the other. The Parameterized Flip Distance problem is to decide if the flip distance between two given triangulations is equal to a given integer k. The previous best FPT algorithm runs in time O⁎(k⋅ck)

A recently introduced operation of geometrical closure on formal languages is investigated from the viewpoint of the algebraic theory of regular languages. Positive varieties V, for which geometrical closure of every language in V is regular, are fully characterised by the property that V is included in W, a known positive variety arising, e.g., in the study of the commutative closure. It is proved

Automatic sequences can be defined by DFAs with output (DFAO) in two natural ways. We propose to consider the minimal size of a corresponding DFAO as the complexity measure of the automatic sequence, for both variants. This paper compares these complexity measures and investigates their properties, such as the relationships with kernel and morphic sequences. There exist automatic sequences for which

Search trees are commonly used to implement access operations to a set of stored keys. If this set is static and the probabilities of membership queries are known in advance, then one can precompute an optimal search tree, namely one that minimizes the expected access cost. For a non-key query, a search tree can determine its approximate location by returning the inter-key interval containing the query

For one-safe Petri nets or condition/event-systems, a process as defined by Carl Adam Petri provides a notion of a run of a system where causal dependencies are reflected in terms of a partial order. Goltz and Reisig have generalised this concept for nets where places carry multiple tokens, by distinguishing tokens according to their causal history. However, this so-called individual token interpretation

Treasure hunt is finding an inert target by a mobile agent. We consider treasure hunt in polygonal terrains with polygonal obstacles. The agent finds the treasure when there is a segment of length at most 1 between them, inside the terrain. The cost of treasure hunt is the length of the agent's trajectory. We investigate the amount of information (advice complexity) needed for treasure hunt at cost

We develop a behavioural theory for monitors, computational entities that passively analyse the runtime behaviour of systems so as to infer properties about them. First, we present a monitor language and an instrumentation relation used for piCalculus process monitoring. We then identify contextual behavioural preorders that allow us to relate monitors according to criteria defined over monitored executions

We introduce a generalization of An.A.Muchink's non-monotonic betting game, the 1/2-betting game, and show that while there is no single computable 1/2-betting strategy that wins on all Martin-Löf non-random sequences, there is a pair that does.

In the modern era of multi-core systems, the main aim is to utilize the cores properly. This utilization can be done by concurrent programming. But developing a flawless and well-organized concurrent program is difficult. Software Transactional Memory Systems (STMs) are a convenient programming interface which assist the programmer to access the shared memory concurrently without worrying about consistency

We investigate exploration algorithms for autonomous mobile robots evolving in uniform ring-shaped networks. Different from the usual Look-Compute-Move (LCM) model, we consider two characteristics: myopia and luminosity. Myopia means each robot has a limited visibility. We consider the weakest assumption for myopia: each robot can only observe its neighboring nodes. Luminosity means each robot maintains

We consider search in an unknown finite 2D square grid by a metamorphic robotic system consisting of anonymous memory-less modules. Each module autonomously moves while executing a common distributed algorithm and the modules collectively form a robotic system by keeping connectivity. The number of shapes of the metamorphic robotic system grows as the number of modules increases, and a shape of the

We present LB-Spiral, a novel distributed directory protocol for shared objects, suitable for large-scale distributed shared memory systems. Each shared object has an owner node that can modify its value. The ownership may change by moving the object from one node to another in response to move requests. The value of an object can be read by other nodes with lookup requests. The distinctive feature