As power grids transition into decentralized Cyber-Physical Power Systems, the digitalization of legacy devices has dramatically multiplied the potential entry points for cyber adversaries. To accurately assess these threats, security models must capture both detailed attack steps and network timing effects. However, obtaining real-world cyber incident data to parameterize these models is rarely possible due to strict privacy and confidentiality constraints within utility companies. To overcome this limitation, we present a simulation-based framework that integrates Attack Graphs (AGs) with the OMNeT++ Discrete Event Simulation environment and Dynamic Bayesian Networks (DBNs). Attack step logic is modeled through Control Finite State Machines, allowing for dynamic interactions between attacker behavior and simulated network components. The simulation automatically generates time-series data used to train AG-derived DBNs used to answer probabilistic queries on attack progression. We present a case study on a Distributed Energy Resource cyberattack which demonstrates that the framework captures complex temporal dependencies and maintains high predictive accuracy supporting cybersecurity assessment for critical energy infrastructures. The code and models implemented in this work are available here: https://github.com/Dosclic98/dbn-sim-learning.git.

We propose an external memory algorithm for the computation of the BWT and LCP array for a collection of sequences. Our algorithm takes the amount of available memory as an input parameter, and tries to make the best use of it by splitting the input collection into subcollections sufficiently small that it can compute their BWT in RAM using an optimal linear time algorithm. Next, it merges the partial BWTs in external memory and in the process it also computes the LCP values. We prove that our algorithm performs O(n AveLcp) sequential I/Os, where n is the total length of the collection, and AveLcp is the average Longest Common Prefix of the collection. This bound is an improvement over the known algorithms for the same task. The experimental results show that our algorithm outperforms the current best algorithm for collections of sequences with different lengths and for collections with relatively small average Longest Common Prefix. In the second part of the paper, we show that our algorithm can be modified to output two additional arrays that, used with the BWT and LCP arrays, provide simple, scan based, external memory algorithms for three well known problems in bioinformatics: the computation of maximal repeats, the all pairs suffix-prefix overlaps, and the construction of succinct de Bruijn graphs. To our knowledge, there are no other known external memory algorithms for these problems.

A widely used class of approximate pattern matching algorithms work in two stages, the first being a filtering stage that uses spaced seeds to quickly discards regions where a match is not likely to occur. The design of effective spaced seeds is known to be a hard problem. In this setting, we propose a family of lossless spaced seeds for matching with up to two errors based on mathematical objects known as perfect rulers. We analyze these seeds with respect to the tradeoff they offer between seed weight and the minimum length of the pattern to be matched. We identify a specific property of rulers, namely their skewness, which is closely related to the minimum pattern length of the derived seeds. In this context, we study in depth the specific case of Wichmann rulers and investigate the generalization of our approach to the larger class of unrestricted rulers. Although our analysis is mainly of theoretical interest, we show that for pattern lengths of practical relevance our seeds have a larger weight, hence a better filtration efficiency, than the ones known in the literature.

Abstract In this work a double exponential time inseparability result is proven for a finitely axiomatizable first order theory Q+. The theory, subset of Presburger theory of addition S+, is the additive fragment of Robinson system Q. We prove that every set that separates Q+ from the logically false sentences of addition is not recognizable by any Turing machine working in double exponential time. The lower bound is given both in the non-deterministic and in the linear alternating time models. The result implies also that any theory of addition that is consistent with Q+—in particular any theory contained in S+—is at least double exponential time difficult. Our inseparability result is an improvement on the known lower bounds for arithmetic theories. Our proof uses a refinement and adaptation of the technique that Fischer and Rabin used to prove the difficulty of S+. Our version of the technique can be applied to any incomplete finitely axiomatizable system in which all of the necessary properties of addition are provable.

User-defined calendars and periodicities are gaining an increasing relevance in AI and DB theory and applications. Thus several representation languages have been introduced to model them. Even focusing the attention on symbolic languages only, several different proposals can be chosen, and the comparisons between them are not trivial at all. In this paper, we propose a lattice of properties about periodicity and use it in order to classify different symbolic approaches in the literature. We then propose a language which covers all the properties in the lattice.

In several areas, including temporal databases, Presburger arithmetic has been chosen as a standard reference to express the semantics of languages representing periodic time, and to study their expressiveness. On the other hand, the proposal of most symbolic languages in the AI literature has not been paired with an adequate semantic counterpart, making the task of studying the expressiveness of such languages and of comparing them a very complex one. In this paper, we first define a representation language which enables us to handle each temporal point as a complex object enriched with all the structure it is immersed in, and then we use it in order to provide a Presburger semantics for classes of symbolic languages coping with periodicity.

This paper addresses the question of the complexity of the decision problem for the theory Th(Q/sub p/) of p-adic numbers. The best known lower bound for the theory is double exponential alternating time with a linear number of alternations. I have designed an algorithm that determines the truth value of sentences of the theory requiring double exponential space. My algorithm is based on techniques used by G.E. Collins (1975) for the theory Th(R) of the reals, and on J. Denef's work (1986) on semi-algebraic sets and cell decomposition for p-adic fields. No elementary upper bound had been previously established.>