arXiv subjects

Natalia Kushik

Publications and source records attributed to Natalia Kushik.

6 recordsLinked to original sources

arXiv2025

Studying homing and synchronizing sequences for Timed Finite State Machines with output delays

The paper introduces final state identification (synchronizing and homing) sequences for Timed Finite State Machines (TFSMs) with output delays and investigates their properties. We formally define the notions of homing sequences (HSs) and synchronizing sequences (SSs) for these TFSMs and demonstrate that several properties that hold for untimed machines do not necessarily apply to timed ones. Furthermore, we explore the applicability of various approaches for deriving SSs and HSs for Timed FSMs with output delays, such as truncated successor tree-based and FSM abstraction-based methods. Correspondingly, we identify the subclasses of TFSMs for which these approaches can be directly applied and those for which other methods are required. Additionally, we evaluate the complexity of existence check and derivation of (shortest) HSs / SSs for TFSMs with output delays.

cs.FL↗

arXiv2022

Dynamic Link Network Emulation: a Model-based Design

This paper presents the design and architecture of a network emulator whose links' parameters (such as delay and bandwidth) vary at different time instances. The emulator can thus be used in order to test and evaluate novel solutions for such networks, before their final deployment. To achieve this goal, different existing technologies are carefully combined to emulate link dynamicity, automatic traffic generation, and overall network device emulation. The emulator takes as an input a formal model of the network to emulate and configures all required software to execute live software instances of the desired network components, in the requested topology. We devote our study to the so-called dynamic link networks, with potentially asymmetric links. Since emulating asymmetric dynamic links is far from trivial (even with the existing state-of-the-art tools), we provide a detailed design architecture that allows this. As a case study, a satellite network emulation is presented. Experimental results show the precision of our dynamic assignments and the overall flexibility of the proposed solution.

cs.NI↗

arXiv2020

On using SMT-solvers for Modeling and Verifying Dynamic Network Emulators

A novel model-based approach to verify dynamic networks is proposed; the approach consists in formally describing the network topology and dynamic link parameters. A many sorted first order logic formula is constructed to check the model with respect to a set of properties. The network consistency is verified using an SMT-solver, and the formula is used for the run-time network verification when a given static network instance is implemented. The z3 solver is used for this purpose and corresponding preliminary experiments showcase the expressiveness and current limitations of the proposed approach.

cs.SE↗

arXiv2020

Preventive Model-based Verification and Repairing for SDN Requests

Software Defined Networking (SDN) is a novel network management technology, which currently attracts a lot of attention due to the provided capabilities. Recently, different works have been devoted to testing / verifying the (correct) configurations of SDN data planes. In general, SDN forwarding devices (e.g., switches) route (steer) traffic according to the configured flow rules; the latter identifies the set of virtual paths implemented in the data plane. In this paper, we propose a novel preventive approach for verifying that no misconfigurations (e.g., infinite loops), can occur given the requested set of paths. We discuss why such verification is essential, namely, how, when synthesizing a set of data paths, other not requested and undesired data paths (including loops) may be unintentionally configured. Furthermore, we show that for some cases the requested set of paths cannot be implemented without adding such undesired behavior, i.e., only a superset of the requested set can be implemented. Correspondingly, we present a verification technique for detecting such issues of potential misconfigurations and estimate the complexity of the proposed method; its polynomial complexity highlights the applicability of the obtained results. Finally, we propose a technique for debugging and repairing a set of paths in such a way that the corrected set does not induce undesired paths into the data plane, if the latter is possible.

cs.NI↗

arXiv2018

Source Code Optimization using Equivalent Mutants

A mutant is a program obtained by syntactically modifying a program's source code; an equivalent mutant is a mutant, which is functionally equivalent to the original program. Mutants are primarily used in \emph{mutation testing}, and when deriving a test suite, obtaining an equivalent mutant is considered to be highly negative, although these equivalent mutants could be used for other purposes. We present an approach that considers equivalent mutants valuable, and utilizes them for source code optimization. Source code optimization enhances a program's source code preserving its behavior. We showcase a procedure to achieve source code optimization based on equivalent mutants and discuss proper mutation operators. Experimental evaluation with Java and C programs demonstrates the applicability of the proposed approach. An algorithmic approach for source code optimization using equivalent mutants is proposed. It is showcased that whenever applicable, the approach can outperform traditional compiler optimizations.

cs.SE↗

arXiv2015

Adaptive Homing is in P

Homing preset and adaptive experiments with Finite State Machines (FSMs) are widely used when a non-initialized discrete event system is given for testing and thus, has to be set to the known state at the first step. The length of a shortest homing sequence is known to be exponential with respect to the number of states for a complete observable nondeterministic FSM while the problem of checking the existence of such sequence (Homing problem) is PSPACE-complete. In order to decrease the complexity of related problems, one can consider adaptive experiments when a next input to be applied to a system under experiment depends on the output responses to the previous inputs. In this paper, we study the problem of the existence of an adaptive homing experiment for complete observable nondeterministic machines. We show that if such experiment exists then it can be constructed with the use of a polynomial-time algorithm with respect to the number of FSM states.

cs.FL↗