Deep neural networks (DNNs) are widely and successfully applied in the field of speaker recognition. However, recent studies reveal that these models are vulnerable to backdoor attacks, where adversaries inject malicious behaviors into victim models by poisoning the training process. Existing attack methods often rely on environmental noise or complex voice transformations, which are typically difficult to implement and exhibit poor stealthiness. To address these issues, this paper proposes two modulation-based backdoor attacks that leverage frequency modulation (FM) and amplitude modulation (AM) to construct audio triggers. In real-world scenarios, regular variations in frequency and amplitude are often imperceptible to human listeners, making the proposed attacks more covert. Experimental results show that our methods achieve high attack success rates in both digital and physical settings, while also demonstrating strong resistance to various state-of-the-art backdoor defenses.

Federated Learning (FL) has emerged as a privacy-preserving paradigm for training machine learning models across distributed edge devices in the Internet of Things (IoT). By keeping data local and coordinating model training through a central server, FL effectively addresses privacy concerns and reduces communication overhead. However, the limited computational power, memory, and bandwidth of IoT edge devices pose significant challenges to the efficiency and scalability of FL, especially when training deep neural networks. Various FL frameworks have been proposed to reduce computation and communication overheads through dropout or layer freezing. However, these approaches often sacrifice accuracy or neglect memory constraints. To this end, in this work, we introduce Federated Learning with Ordered Layer Freezing (FedOLF). FedOLF consistently freezes layers in a predefined order before training, significantly mitigating computation and memory requirements. To further reduce communication and energy costs, we incorporate Tensor Operation Approximation (TOA), a lightweight alternative to conventional quantization that better preserves model accuracy. Experimental results demonstrate that over non-iid data, FedOLF achieves at least 0.3%, 6.4%, 5.81%, 4.4%, 6.27% and 1.29% higher accuracy than existing works respectively on EMNIST (with CNN), CIFAR-10 (with AlexNet), CIFAR-100 (with ResNet20 and ResNet44), and CINIC-10 (with ResNet20 and ResNet44), along with higher energy efficiency and lower memory footprint.

With the rapid development of blockchain technology, smart contract applications have become increasingly widespread. However, vulnerabilities in contracts may be exploited by attackers, causing serious financial losses. In recent years, learning-based approaches have gained prominence for their accuracy and efficiency by automatically extracting explicit syntactic or semantic features from a large number of smart contracts with minimal manual intervention. In this article, we conduct a comprehensive analysis and ultimately select 61 scientific publications to provide researchers, especially beginners, with a comprehensive understanding of the learning-based detection process and guidance on selecting appropriate code representations. We first introduce common types of vulnerabilities, detail uncovered vulnerabilities, and summarize datasets used in learning-based methods. Then, we elaborate on the general process of learning-based detection and classify existing publications based on code representations, including sequence, tree, graph, and mixed features. Finally, we summarize the progress of existing work and explore future research directions in this field.

We propose Meta-DPMAPPO /metə,dipi'mæpəʊ/, a a metaverse multi-user service migration framework that combines Multi-Agent Proximal Policy Optimization (MAPPO) with Differential Privacy (DP)-enabled dual-domain perturbation. To maintain usability, we incorporate trajectory topology constraints that balance privacy strength with data availability. The framework enables dynamic service migration, i.e., transferring services to follow mobile users, to ensure low-latency access while safeguarding sensitive user data. We design a migration strategy with multiple migration actions (i.e.,reuse,follow, andnomigration) to minimize global delay and improve resource utilization. We conduct a series of experiments using a combination of public, collected, and synthetic datasets. The results demonstrate that our approach significantly reduces global migration delay in multi-user environments while ensuring privacy protection, and adapts well to different metaverse application scenarios.

The metaverse is a pioneering cyber-physical space that seamlessly blends the physical and virtual worlds, demanding a fully immersive and highly interactive user experience. However, existing communication designs and traditional offloading and allocation approaches fall short of meeting the dynamic network conditions and real-time performance demands of the metaverse. To tackle these challenges, we develop a wireless transmission architecture optimized for metaverse computation offloading and resource allocation. This design leverages the Rayleigh fading and Multiple Input Multiple Output (MIMO) technology to optimize transmission paths, enhancing the reliability and efficiency of signal transmission in high-concurrency connections. We further introduce MetaTMCO (MetaTransformer andMAPPO basedComputationOffloading), a dynamic online computation offloading and resource allocation joint optimized method that meets critical QoS requirements for metaverse applications. MetaTMCO uses a metric named Interaction Frequency (IF) to evaluate resource competition between users and resource interaction between users and the environment, combining QoS to maximize utility under resource constraints. By integrating a Transformer-based encoder-decoder within the Multi-Agent Proximal Policy Optimization (MAPPO) algorithm, MetaTMCO mitigates inefficiencies from partial observations, enabling dynamic optimization of real-time fast offloading strategies across multiple agents. Experimental results demonstrate that MetaTMCO significantly outperforms other approaches in metaverse environments, achieving superior strategy optimization and resource efficiency.

Ensuring the safety of autonomous driving systems (ADS) in a cost-effective and efficient manner remains a critical challenge. Existing law-guided scenario generation approaches are typically limited to a narrow subset of legal rules, resulting in insufficient scenario diversity, and search-based methods often struggle with large and sparse search spaces. To address these limitations, we propose SLaFE (Semantic Law Modeling and Fuzzing based on Cooperative Evolution), a novel traffic violation scenario generation framework designed to systematically evaluate the safety of ADS. SLaFE harnesses the reasoning capabilities of large language models (LLMs) to convert traffic laws into structured scenario constraints. These scenarios are then optimized via a cooperative evolutionary fuzzing algorithm that explores the parameter space to identify boundary cases likely to trigger abnormal ADS behaviors. We evaluate SLaFE on the Apollo platform within the LGSVL simulator using ten realworld traffic regulations. Experimental results show that SLaFE successfully triggered all 10 types of traffic law violations (10/10), outperforming the best existing method, VioHawk (9/10), while others detected no more than 3. Moreover, SLaFE achieved an average triggering time of 5.1 minutes per law type, significantly faster than VioHawk (9.0 minutes) and other baselines. These results highlight SLaFE’s effectiveness in discovering diverse and critical law-violating scenarios for ADS testing.

Deep neural network (DNN) based text intelligence softwares have proliferated and have been widely used. However, they face challenges such as robustness. Testing is essential to DNNs in real-world applications. Researchers have proposed various testing techniques for generating test cases. With the black-box hard-label setup where only the output label of the DNN is accessible, related studies mainly concentrated on generating the new text test case by iteratively perturbing single initial test case, which limits the effectiveness. To address this issue, this paper proposes a new text test case generation method MVGText (Momentum and Variance Guided hard-label Text test case generation) for text-oriented DNN, which generates high-quality text test cases by searching based on multiple initial test cases. Firstly, multiple initial text test cases are generated randomly, in which global fixed word replacement is employed to enhance the success rate. Then, momentum and variance are applied to guide the search for the more imperceptible test case. Finally, greedy optimization is used to obtain a higher quality test case. Experimental evaluation shows that MVGText achieves an average post-test success rate of 1.4%. Furthermore, the test cases generated by MVGText exhibit the highest similarity to the original text compared to other comparative methods.

While smart contracts, as automatic processing programs for decentralized applications deployed on the blockchain, have gained widespread attention, their vulnerabilities have also led to significant economic losses. To address this security issue, researchers have proposed various approaches for locating vulnerabilities in smart contracts. However, most of them are designed to identify vulnerable smart contracts within a blockchain-based application. Only a few approaches adopt deep learning techniques to locate the exact line containing the reentrancy vulnerability based on Ethereum smart contracts’ source code. In this paper, we focus on the bytecode of Ethereum smart contracts and propose DeepLocator, a deep learning-based two-phase locator designed to pinpoint code-line-level reentrancy vulnerabilities. In the detection phase, DeepLocator constructs an attributed control flow graph extracted from the smart contract’s opcodes, and applies graph neural networks (GNNs) to determine whether a contract contains reentrancy vulnerabilities. In the localization phase, DeepLocator employs a model explainer of GNNs to rank the opcodes of each vulnerable smart contract according to their impact on the detection phase’s results, and then maps them back to the source code with the output of ranked suspicious statements. Empirical experiments conducted on widely used datasets of reentrancy vulnerabilities validate the efficacy of our locator. DeepLocator outperforms baseline traditional and learning-based detection approaches by 28.7% and 3.5%, respectively. Moreover, it pinpoints 20.0%, 61.1%, and 74.5% vulnerabilities within the top 1, 5, and 10 ranked suspicious statements, respectively.

With the rapid development of blockchain technology, smart contracts have become a key innovation, offering de-centralized, transparent, and automated solutions across various industries. However, their widespread adoption has also exposed significant security vulnerabilities, leading to substantial financial losses. Traditional vulnerability detection methods are limited in terms of automation and efficiency due to their reliance on predefined knowledge. Although deep learning-based methods show promise, their effectiveness is hindered by the need for high-quality labeled datasets. Recently, large language models (LLMs) have been applied to the detection of vulnerabilities in smart contracts due to their powerful code understanding capabilities. However, their lack of domain-specific knowledge limits their ability to grasp the structure information and context of smart contracts, leading to suboptimal detection results. This paper proposes an approach driven by LLMs to detect vulnerabilities in Ethereum smart contracts, combining logic Abstract Semantic Graph (logicASG) reasoning with In-Context Learning (ICL). Our approach integrates the contract’s logicASG to improve the code understanding of LLMs, retrieves the logicASG’s most similar graph to provide domain-specific knowledge, and designs a Chain-of-Thought (CoT) based prompt template to compose complex vulnerability detection problem. Experimental evaluations conducted on a recently published dataset consisting of 1093 smart contracts validate the efficacy of our approach. Compared to current advanced approaches, our approach achieves an average accuracy improvement of 24.05%, and reduces detection time per contract by 111.69 seconds.

We propose a new workflow task execution time prediction approach, DAG-FGL, by integrating Flash attention mechanism with a GraphLSTM model. It addresses the challenge of low task execution time prediction accuracy in the presence of complex dependencies among workflow subtasks. The GraphLSTM model captures and conveys subtask dependencies through the adjacency matrix of sub task relationships modeled as a directed acyclic graph (DAG). The Flash attention mechanism enhances the model by incorporating customized positional encoding of subtask priority. The encoding ensures that the model accurately reflects each subtask's importance and relative order when calculating attention weight. Therefore, DAG- FG L can more accurately predict task execution time in the context of complex dependencies. Experimental results show that DAG-FGL outperforms the best-performing baseline model. It achieves 7.82 % to 44.52 % improvements in prediction accuracies over the best-performing baselines across three cloud workflow datasets of varying lengths.

Mobile edge computing (MEC) enables cooperative vehicle infrastructure systems (CVIS) to provide computational services to vehicles via roadside units. However, the increasing complexity of intelligent vehicles leads to the generation of numerous delay-sensitive tasks, presenting significant challenges for computation offloading. Furthermore, frequent interactions between intelligent vehicles and servers during the offloading process exacerbate privacy risks. In this paper, we propose a novel resource discovery approach, which determines the priority of offloading tasks based on an incentive strategy and constructs a task queue to optimize resource utilization. To facilitate optimal task offloading decisions, we employ a federated reinforcement learning algorithm that integrates dynamic differential privacy, addressing the dynamic nature of privacy protection requirements and enhancing the security of edge nodes. Through simulation, we demonstrate that our proposed algorithm outperforms traditional approaches by effectively reducing task execution latency and preserving vehicular privacy. The experimental findings highlight the potential of our approach to significantly improve task offloading performance in CVIS.

Deep learning (DL) components have been broadly applied in diverse applications. Similar to traditional software engineering, effective test case generation methods are needed by industry to enhance the quality and robustness of these deep learning components. To this end, we propose a novel automatic software testing technique, TAEFuzz (Automatic Fuzz -Testing via T ransferable A dversarial E xamples), which aims to automatically assess and enhance the robustness of image-based deep learning (DL) systems based on test cases generated by transferable adversarial examples. TAEFuzz alleviates the over-fitting problem during optimized test case generation and prevents test cases from prematurely falling into local optima. In addition, TAEFuzz enhances the visual quality of test cases through constraining perturbations inserted into sensitive areas of the images. For a system with low robustness, TAEFuzz trains a low-cost denoising module to reduce the impact of perturbations in transferable adversarial examples on the system. Experimental results demonstrate that the test cases generated by TAEFuzz can discover up to 46.1% more errors in the targeted systems, and ensure the visual quality of test cases. Compared to existing techniques, TAEFuzz also enhances the robustness of the target systems against transferable adversarial examples with the perturbation denoising module.

Given that smart contracts execute transactions worth hundreds of millions of dollars daily, the issue of smart contract security has attracted considerable attention over the past few years. Traditional methods for detecting vulnerabilities heavily rely on manually developed rules and features, leading to the problems of low accuracy, high false positives, and poor scalability. Although deep learning-inspired approaches were designed to alleviate the problem, most of them rely on monothetic features, which may result in information incompetence during the learning process. Furthermore, the lack of available labeled vulnerability datasets is also a major limitation. To address these issues, we collect and construct a dataset of five labeled smart contract vulnerabilities, and proposeDeepFusion, a vulnerability detection method that fuses code representation information, including program slice information and abstraction syntax tree (AST) structured information. First, we develop automated tools to extract contract vulnerability slicing information from source code, and extract structured information from source code-converted AST. Second, code features and global structured features are fused into the data. Finally, the fused data are input into the Bidirectional Long Short-Term Memory+ Attention (BiLSTM+ATT) model for smart contract vulnerability detection. The BiLSTM model can capture long-term dependencies in both directions and is more suitable for processing serialized information generated byDeepFusion, while the attention mechanism can highlight the characteristic information of vulnerabilities. We conducted experiments via collecting a real smart contract dataset. The experimental results show that our method significantly outperforms the existing methods in detecting the vulnerabilities ofreentrancy,timestamp dependence,integer overflow and underflow,Use tx.origin for authentication, andUnprotected Self-destruct Instructionby 6.36%, 6.42%, 16.5%, 21.29%, and 25.05%, respectively. To the best of our knowledge, the latter two vulnerabilities are the first to be detected using deep learning methods.

In mobile edge computing (MEC), mobile users can offload tasks to edge nodes to alleviate local computational loads, leveraging the computing capabilities of edge nodes. However, users' high mobility and temporal variability pose challenges in dynamically allocating mobile users to optimize perceived Quality of Service (QoS). To address this challenge, this paper proposes an adaptive ant colony algorithm for user allocation decisions. This method constructs hidden mobility fitness relationships between users and servers based on user movement trajectories. It utilizes an improved adaptive ant colony algorithm to adjust fitness values automatically and optimize user allocation. The goal is to maximize overall user satisfaction under resource constraints while minimizing user allocation costs. Experimental analysis demonstrates that the proposed method achieves higher user allocation rates and effectively utilizes available resources on edge servers.

The widespread use of deep neural networks (DNNs) in image classification sofwares underlines the importance of the robustness. Researchers have proposed sparse adversarial attack methods for generating test cases, which add pixel-level perturbations to construct the test case to mislead the target model. However, the existing methods have certain limitations, such as high time cost, poor flexibility, and poor quality of the test cases. To address these issues, we propose a gradient-guided test case generation method (GGTM) to evaluate the robustness of image classification software. The method firstly identifies the key region in the image based on the gradient-weighted class activation mapping (Grad-CAM) and the prediction confidence of the target model on the input image. In the key region, it selects a set of pixels as candidate perturbation pixels according to the gradient value and the change of loss function. Then perturbations are added to the candidate perturbation pixels after applying a random dropout strategy to reduce some candidate perturbation pixels which is used to avoid local optimum. For the initially constructed test case which can mislead the target model, after removing redundant and unimportant perturbations, perturbations are re-added to optimize the test case. Experiments show the effectiveness of GGTM, which achieves 100% attack success rate. And the test cases generated by GGTM have the best perturbation sparsity. Furthermore, compared with the baseline method SparseAG which achieves optimal perturbation sparsity among the baseline methods, GGTM significantly improves the efficiency.

With the growing prevalence of deep learning in the speech area, speech recognition, voice control, and related applications have become integral parts of people's lives. However, the rise of malicious third-party platforms has introduced significant security concerns, particularly through backdoor attacks. These attacks implant triggers that manipulate speech recognition models to produce specific labels, thereby compromising the system's integrity. Studying speech backdoor attacks is crucial for evaluating the security of speech recognition software, and iden-tifying and addressing potential vulnerabilities. Existing methods for speech backdoor attacks usually employ fixed perturbations as triggers. However, these perturbations may be discernible to the human ear, making them easily detectable. To address this issue, we propose a frequency domain-embedded backdoor attack method based on echo hiding. Echo hiding is a steganography technique based on audio. This method embeds hidden information into the frequency spectrum of the echo signal, leveraging the masking property of the human auditory system. It is difficult to arouse suspicion or detect the presence of hidden information since echo is perceived as a natural phenomenon in auditory perception. Furthermore, it does not cause a significant decrease in audio quality. Experimental results show the effectiveness of our method in different settings.

Scribble-supervised semantic segmentation presents a cost-effective training method that utilizes annotations generated through scribbling. It is valued in attaining high performance while minimizing annotation costs, which has made it highly regarded among researchers. Scribble supervision propagates information from labeled pixels to the surrounding unlabeled pixels, enabling semantic segmentation for the entire image. However, existing methods often ignore the features of classified pixels during feature propagation. To address these limitations, this paper proposes a prototype-based feature augmentation method that leverages feature prototypes to augment scribble supervision. Experimental results demonstrate that our approach achieves state-of-the-art performance on the PASCAL VOC 2012 dataset in scribble-supervised semantic segmentation tasks. The code is available at https://github.com/TranquilChan/PFA.

The emergence of the metaverse signifies a paradigm shift in Internet technology, offering a comprehensive virtual social platform spanning various domains such as social interaction, gaming, healthcare, and tourism. This new era of the metaverse is facilitated by advancements in next-generation digital technologies including edge computing, artificial intelligence, virtual reality, augmented reality, and blockchain. In the metaverse, the quantity and variety of services requested by users may surpass those in other environments, and existing work cannot be applied to metaverse QoS (Quality of Service) optimization. To address this problem, this paper proposes Meta-PPO, an optimization method for enhancing the QoS of metaverse services using reinforcement learning. Firstly, metaverse services are categorized into virtual scene services and meta-services, providing a comprehensive framework for analysis. Secondly, Meta-PPO, based on the proximal policy optimization algorithm, is introduced to optimize the QoS of metaverse services. This method effectively balances the objectives of minimizing average delay and maximizing resource utilization of mobile devices by making informed offloading decisions for the identified service categories. Simulation results demonstrate the superiority of the proposed method over existing techniques, showcasing its suitability and effectiveness for enhancing the QoS of metaverse service.

Mobile edge computing (MEC) relies on offloading tasks to edge nodes to avoid delays and failures caused by local computing. However, developing efficient offloading decisions is challenging, as it involves addressing the intricacies of tasks and the instability of edge node resources(e.g. available computer resources, memory, and bandwidth). In this paper, we propose a novel approach to tackle the problem of task offloading. Our approach involves dividing tasks into smaller units and considering the correlations between these sub-tasks. To make optimal offloading decisions, we employ a deep reinforcement learning algorithm that takes into account user movement patterns and the availability of resources at edge nodes. Through simulations, we demonstrate that our proposed algorithm outperforms several existing algorithms in terms of offloading decisions. It effectively reduces task execution delays and energy costs. These findings highlight the potential of our approach in improving the performance of task offloading in MEC systems.

Abstract The growing popularity of smart contracts in various areas, such as digital payments and the Internet of Things, has led to an increase in smart contract security challenges. Researchers have responded by developing vulnerability detection tools. However, the effectiveness of these tools is limited due to the lack of authentic smart contract vulnerability datasets to comprehensively assess their capacity for diverse vulnerabilities. This paper proposes a Deep Learning‐based Smart contract vulnerability Generation approach (SGDL) to overcome this challenge. SGDL utilizes static analysis techniques to extract both syntactic and semantic information from the contracts. It then uses a classification technique to match injected vulnerabilities with contracts. A generative adversarial network is employed to generate smart contract vulnerability fragments, creating a diverse and authentic pool of fragments. The vulnerability fragments are then injected into the smart contracts using an abstract syntax tree to ensure their syntactic correctness. Our experimental results demonstrate that our method is more effective than existing vulnerability injection methods in evaluating the contract vulnerability detection capacity of existing detection tools. Overall, SGDL provides a comprehensive and innovative solution to address the critical issue of authentic and diverse smart contract vulnerability datasets.

Abstract With the widespread application of smart contracts, there is a growing concern over the quality assurance of smart contracts. The data flow testing is an important technology to ensure the correctness of smart contracts. We propose an approach named IABC‐TCG (Improved Artificial Bee Colony‐Test Case Generation) to generate test cases for the data flow testing of smart contracts. With a dominance relations‐based fitness function, an improved artificial bee colony algorithm is used to generate test cases, in which the bee colony search coefficient is adaptively adjusted to improve the effectiveness and efficiency of the search. In addition, an improved test case selection and updation strategy is used to avoid unnecessary test cases. The experimental results show that IABC‐TCG achieves 100% coverage for all the test requirements on a dataset of 30 smart contracts and outperforms the baseline approaches in terms of the number of test cases and the execution time. Performing tests with the generated test cases, IABC‐TCG can find more errors with less test cost.

Deep neural networks (DNNs) have been widely and successfully adopted and deployed in various applications of speech recognition. Recently, a few works revealed that these models are vulnerable to backdoor attacks, where the adversaries can implant malicious prediction behaviors into victim models by poisoning their training process. In this paper, we revisit poison-only backdoor attacks against speech recognition. We reveal that existing methods are not stealthy since their trigger patterns are perceptible to humans or machine detection. This limitation is mostly because their trigger patterns are simple noises or separable and distinctive clips. Motivated by these findings, we propose to exploit elements of sound (e.g., pitch and timbre) to design more stealthy yet effective poison-only backdoor attacks. Specifically, we insert a short-duration high-pitched signal as the trigger and increase the pitch of remaining audio clips to ‘mask’ it for designing stealthy pitch-based triggers. We manipulate timbre features of victim audio to design the stealthy timbre-based attack and design a voiceprint selection module to facilitate the multi-backdoor attack. Our attacks can generate more ‘natural’ poisoned samples and therefore are more stealthy. Extensive experiments are conducted on benchmark datasets, which verify the effectiveness of our attacks under different settings (e.g., all-to-one, all-to-all, clean-label, physical, and multi-backdoor settings) and their stealthiness. Our methods achieve attack success rates of over 95% in most cases and are nearly undetectable. The code for reproducing main experiments are available at https://github.com/HanboCai/BadSpeech_SoE.

With the rapid development of 5G technologies, the demand of quality of service (QoS) from edge users, including high bandwidth and low latency, has increased dramatically. QoS within a mobile edge network is highly dependent on the allocation of edge users. However, the complexity of user movement greatly challenges edge user allocation, leading to privacy leakage. In addition, updating massive data constantly in a dynamic mobile edge network also crucial to ensure efficiency. To address these challenges, this paper proposes a dynamic QoS optimization strategy (MENIFLD_QoS) in mobile edge networks based on incremental learning and federated learning.MENIFLD_QoSoptimizes service cache in edge regions and allocates edge servers to edge users according to the locations of edge servers accessed by edge users in mobile scenarios. While optimizing regional service quality, the system can effectively protect user privacy. In addition, for dynamic incremental data,MENIFLD_QoStrains updated data based on the strategy of incremental learning hence significantly improves optimization speed. Experimental results on an edge QoS dataset show that the proposed strategy achieves global optimization in both multi-variable and multi-peak user allocation scenarios and notably enhances the training efficiency of the regional invocation model.

This paper presents a novel probabilistic Quality of Service (QoS) monitoring method named DLSTM-BRPM (Double Long Short Term Memory (DouLSTM-Den) based Bayesian Runtime Proactive Monitoring) to accurately and efficiently monitor QoS in a mobile edge environment. This method consists of a DouLSTM-Den model and a Gaussian Hidden Bayesian classifier. The DouLSTM-Den model aims to predict a user’s future movement trajectory in real time and proactively monitor the spatio-temporal QoS performance of services based on the predicted trajectory. The Gaussian Hidden Bayesian classifier is employed to accurately monitor QoS by constructing parent attributes to reduce the interdependence between QoS attributes. Our experiments based on public synthetic datasets demonstrate the effectiveness of the proposed method over state-of-the-art solutions. We also conducted experiments in a real-world edge environment to validate the feasibility of the proposed method.

We propose an innovative approach named MEC-RDESN /mek”r:dI’saIn/ (MECQoS forecasting based onRegion recognition andDynamicEchoStateNetwork) enabling mobility-aware and swift QoS forecasting in the mobile edge computing environment. MEC-RDESN offers efficient QoS forecasting while maintaining high accuracy. We can identify the edge region to which a user belongs in real time while moving by leveraging mobile sensing technology. We employ adynamic echo state networkcharacterized by multi-service adaptability to retain information about services invoked by users to ensure real-time training and forecasting accuracy. Our approach is validated through a series of experiments using both public and collected datasets. The experiments demonstrate that MEC-RDESN achieves the goal of fast forecasting while ensuring its forecasting accuracy in diverse application scenarios.

Federated learning provides privacy protection to the collaborative training of global model based on distributed private data. The local private data is often in the presence of long-tailed distribution in reality, which downgrades the performance and causes biased results. In this paper, we propose a dynamic adaptive federated learning optimization algorithm with the Grey Wolf Optimizer and Markov Chain, named FedWolf, to solve the problems of performance degradation and result bias caused by the local long-tailed data. FedWolf is launched with a set of randomly initialized parameters instead of a shared parameter employed by existing methods. Then multi-level participants are elected based on the F1 scores calculated from the uploaded parameters. A dynamic weighting strategy based on the participant level is used to adaptively update parameters without artificial control. The above parameter updating is modelled as a Markov Process. After all communication rounds are completed, the future performance (including the probability of each participant is elected as different participant level) of participants is predicted through the historical Markov states. Finally, the probability of each participant is elected as the level 1 is used as the contribution weight and the global model is obtained through dynamic contribution weight aggregating. We introduce the Gini index to evaluate the bias of classification results. Extensive experiments are conducted to validate the effectiveness of FedWolf in solving the problems of performance cracks and categorization result bias as well as the robustness of adaptive parameter updating in resisting outliers and malicious users.

Mobile devices commonly offload latency-sensitive applications to edge servers to meet low-latency requirements. However, existing studies overlook dependency and application hit ratio considerations, hindering effective offloading for multi-applications and multi-tasks. To this end, this article proposes a Dependent task offloading and Service placement Optimization (DSO) method to maximize the application hit ratio, thereby providing high-quality service. The proposed DSO includes Improved Multi-Agent Q-Learning (IMAQL) and greedy algorithms. IMAQL optimizes service placement via Q-learning, while the greedy algorithm schedules task offloading. Extensive experiments on public datasets demonstrate that the DSO method enhances the application hit ratio by 4.7% to 11.7% and reduces the completion time by about 3.4% to 4.9% compared to alternative approaches.

Although many tools have been developed to detect anomalies in smart contracts, the evaluation of these analysis tools has been hindered by the lack of adequate anomalisticreal-world contracts(i.e., smart contracts with addresses on Ethereum to achieve certain purposes). This problem prevents conducting reliable performance assessments on the analysis tools. An effective way to solve this problem is to inject anomalies intoreal-world contractsand automatically label the locations and types of the injected anomalies.SolidiFI, as the first and only tool in this area, was developed to automatically inject anomalies into Ethereum smart contracts. However,SolidiFIis subject to the limitations from its methodologies (e.g., its injection accuracy and authenticity are low). To address these limitations, we propose an approach calledSCAnoGenerator.SCAnoGeneratorsupports Solidity 0.5.x, 0.6.x, 0.7.x and enables automatic anomaly injection for Ethereum smart contracts via analyzing the contracts’ control and data flows. Based on this approach, we develop an open-source tool, which can inject 20 types of anomalies into smart contracts. The extensive experiments show thatSCAnoGeneratoroutperformsSolidiFIon the number of injected anomaly types, injection accuracy, and injection authenticity. The experimental results also reveal that existing analysis tools can only partially detect the anomalies injected bySCAnoGenerator.

With the development of blockchain technology, an increasing number of users are adopting cross-blockchain smart contracts, which necessitates effective testing methods due to digital asset security concerns. However, few work specifically tailored for cross-chain smart contracts. In this paper, we propose a test case generation method for cross-chain contracts based on the ant colony algorithm. This method conducts data flow analysis on the cross-chain smart contract to identify the critical information related statements. These statements are then subjected to mutation operations to create mutants. Subsequently, test cases are generated with an improved ant colony algorithm to kill as many mutants as possible. Theoretically, this method can effectively detect faults in critical information related handling in cross-chain smart contracts.

While process mining has gained much attention in the past decade, surprisingly, discovering structural errors (i.e., deadlock and lack of synchronization) from event logs has seldom been studied. Since event logs may involve erroneous event occurrences caused by unsynchronized activities, discovering deadlocks and lack of synchronization errors may influence each other. To this end, we first extract from the original event log two independent event logs which are employed to discover deadlocks and lack of synchronization errors, respectively. We then discard the erroneous event occurrences in the two event logs, from which our event relation based mining rules can discover the corresponding structural errors. We have implemented our approach, and the experimental results corroborate that our approach can effectively and efficiently discover process structural errors from the event logs involving sufficient event sequences.

The blockchain ecosystem is expanding as a result of advancements in blockchain technology and the emergence of BaaS (Blockchain as a Service) platforms. Smart contracts are designed to carry out diverse business operations, but there is a risk of Ponzi schemes being concealed within them. These schemes masquerade as investment agreements and deceive users, resulting in substantial losses for the blockchain community. Detecting Ponzi schemes in smart contracts is crucial. This study introduces a machine learning approach to identify Ponzi schemes by extracting features from smart contracts using the control flow graph. During the construction of the control flow graph for the smart contract’s bytecode, elements unrelated to its functionality are identified and eliminated. We utilize the control flow graph to extract n-gram Term Frequency and n-gram Term Frequency-Inverse Document Frequency features. These features are respectively employed to construct a Random Forest model for Ponzi scheme detection. To address the issue of imbalanced samples, the SVM_SMOTE oversampling algorithm is applied to balance the number of positive and negative samples. The results from experiments conducted on a real-world dataset demonstrate the effectiveness of our approach. The feature extraction method based on the control flow graph outperforms the method based on continuous text. Additionally, the Random Forest model utilizing SVM_SMOTE outperforms four existing models.

The widespread adoption of DNNs in NLP software has highlighted the need for robustness. Researchers proposed various automatic testing techniques for adversarial test cases. However, existing methods suffer from two limitations: weak error-discovering capabilities, with success rates ranging from 0% to 24.6% for BERT-based NLP software, and time inefficiency, taking 177.8s to 205.28s per test case, making them challenging for time-constrained scenarios. To address these issues, this paper proposes LEAP, an automated test method that uses LEvy flight-based Adaptive Particle swarm optimization integrated with textual features to generate adversarial test cases. Specifically, we adopt Levy flight for population initialization to increase the diversity of generated test cases. We also design an inertial weight adaptive update operator to improve the efficiency of LEAP's global optimization of high-dimensional text examples and a mutation operator based on the greedy strategy to reduce the search time. We conducted a series of experiments to validate LEAP's ability to test NLP software and found that the average success rate of LEAP in generating adversarial test cases is 79.1%, which is 6.1% higher than the next best approach (PSOattack). While ensuring high success rates, LEAP significantly reduces time overhead by up to 147.6s compared to other heuristic-based methods. Additionally, the experimental results demonstrate that LEAP can generate more transferable test cases and significantly enhance the robustness of DNN-based systems.

Abstract Test case generation techniques based on adversarial examples are commonly used to enhance the reliability and robustness of image‐based and text‐based machine learning applications. However, efficient techniques for speech recognition systems are still absent. This paper proposes a family of methods that generate targeted adversarial examples for speech recognition systems. All are based on thefirefly algorithm (F), and are enhanced withgaussmutations and / orgradientestimation (F‐GM, F‐GE, F‐GMGE) to fit the specific problem of targeted adversarial test case generation. We conduct an experimental evaluation on three different types of speech datasets, includingGoogle Command,Common VoiceandLibriSpeech. In addition, we recruit volunteers to evaluate the performance of the adversarial examples. The experimental results show that, compared with existing approaches, these approaches can effectively improve the success rate of the targeted adversarial example generation. The code is publicly available at https://github.com/HanboCai/FGMGE .

Smart contracts are commonly deployed for safety-critical applications, the quality assurance of which has been a vital factor. Test cases are standard means to ensure the correctness of data flows in smart contracts. To more efficiently generate test cases with high coverage, we propose an improved genetic algorithm-based test-case generation approach for smart contract data flow testing. Our approach introduces the theory of particle swarm optimization into the genetic algorithm, which reduces the influence brought by the randomness of genetic operations and enhances its capability to find global optima. A set of 30 real smart contracts deployed on Ethereum and GitHub is collected to perform the experimental study, on which our approach is compared with three baseline approaches. The experimental results show that, in most cases, the coverage of the test cases generated by our approach is significantly higher than the baseline approaches with relatively lower numbers of iterations and lower execution time.

We propose a novel privacy-aware Quality of Service (QoS) forecasting approach in the mobile edge environment Edge-PMAM (Edge QoS forecasting with Public Model and Attention Mechanism). Edge-PMAM can make real-time, accurate and personalized QoS forecasting on the premise of user privacy preservation. Edge-PMAM comprises a public model for privacy-aware QoS forecasting in an edge region and a private model for personalized QoS forecasting for an individual user. An attention mechanism atop Long Short-Term Memory and an automated edge region division solution are devised to enhance the prediction accuracy of the public and private models. We conduct a series of experiments based on public and self-collected data sets. The results demonstrate that our approach can effectively improve forecasting performance and protect user privacy.

With the rising prominence of smart contracts, security attacks targeting them have increased, posing severe threats to their security and intellectual property rights. Existing simplistic datasets hinder effective vulnerability detection, raising security concerns. To address these challenges, we proposeBiAn, a source code level smart contract obfuscation method that generates complex vulnerability test datasets.BiAnprotects contracts by obfuscating data flows, control flows, and code layouts, increasing complexity and making it harder for attackers to discover vulnerabilities. Our experiments with buggy contracts showed an average complexity enhancement of approximately 174% after obfuscation. Decompilers Vandal and Gigahorse had total failure rate increments of 38.8% and 40.5% respectively. Obfuscated contracts also decreased vulnerability detection rates in more than 50% of cases for ten widely-used static analysis detection tools.

With the widespread use of smart contracts, security incidents caused by improper programming have drawn increasing attention. Data flow correctness is a fundamental and vital requirement for smart contracts. Although test cases generated by existing approaches for data flow testing of smart contracts can achieve certain coverage, not all def-use (definitionuse) pairs are covered, which may result in some errors not being detected. To further improve the adequacy and efficiency of testing, we present an approach named TCG-Re (T est C ase G eneration Combined with Data Flow R eduction) to generate test cases for data flow testing of smart contracts. Data flow reduction is performed to reduce redundant def-use pairs and obtain the final test requirements in a smart contract. The test case generation process is optimized to improve the coverage of the generated test cases for the def-use pairs. We collect 30 smart contracts of different scales to perform experimental evaluation. The result shows that, compared with other existing approaches, TCG-Re can not only achieve full coverage for most contracts, but also be more efficient. In addition, TCG-Re is also effective for discovering several types of errors in smart contracts.

Ethereum smart contracts face serious security problems, which not only cause huge economic losses, but also destroy the Ethereum credit system. To solve this problem, code obfuscation techniques are applied to smart contracts to improve their complexity and security. However, the current source code obfuscation methods have insufficient anti-decompilation ability. Therefore, we propose a novel bytecode obfuscation approach called BOSC based on four kinds of bytecode obfuscation techniques, which is directed at solidity. The experimental results show that, after the bytecode obfuscation, the failure rate of decompilation tools is over 99% and only a small amount of gas is consumed.

We propose a novel privacy-aware Quality of Service (QoS) forecasting approach in the mobile edge environment – Edge-PMAM (Edge QoS forecasting with Public Model and Attention Mechanism). Edge-PMAM can make realtime, accurate and personalized QoS forecasting on the premise of user privacy preservation. Edge-PMAM comprises a public model for privacy-aware QoS forecasting in an edge region and a private model for personalized QoS forecasting for an individual user. An attention mechanism atop Long Short-Term Memory and an automated edge region division solution are devised to enhance the prediction accuracy of the public and private models. We conduct a series of experiments based on public and self-collected data sets. The results based on public and self-collected data sets demonstrate that our approach can effectively improve forecasting performance and protect user privacy.

Process mining aims at discovering behavioral knowledge of business processes from their event logs, which has received an increasing attention in the era of cloud computing and big data. Surprisingly, to date, discovering structural errors (e.g., deadlocks and lack of synchronization) from event logs has not been considered in state-of-the-art process mining techniques. Moreover, existing process discovery approaches cannot be directly applied to event logs of processes with structural errors due to erroneous event occurrences caused by unsynchronized activities. To address this problem, we first preprocess the event log to obtain two separate event logs that are used to discover deadlocks and lack of synchronization, respectively. Erroneous event occurrences caused by unsynchronized activities are discarded in the two processed event logs, from which our error mining algorithms can discover all process fragments involving structural errors, without the need to obtain the overall process first. We implement our approach in a ProM plugin and evaluate it on event logs of real-life business processes, the results of which demonstrate that our approach can effectively and efficiently discover deadlocks and lack of synchronization if event logs contain sufficient event sequences.

Quality of Service (QoS) is well acknowledged as a decisive means for ascertaining the performance of third-party Web services. QoS has high uncertainty in complex and dynamic network environments. QoS monitoring is considered as one of the most effective techniques to detect QoS violations at runtime. However, existing QoS monitoring approaches only consider single QoS attribute and do not provide a promising solution for comprehensively monitoring multivariate QoS attributes. To overcome this problem, a novel QoS monitoring approach, named M-BSRM (MultivariateBayeSianRuntimeMonitoring), is proposed. First, M-BSRM adopts the point mutual information theory to initialize the weights of different environmental impact factors and solves the problem of uneven distribution between classes brought by traditional algorithms. Second, each single QoS attribute is integrated with user preference using the information fusion theory. Finally, a Bayesian classifier is used to comprehensively evaluate multivariate QoS attributes at runtime. The experimental results on both the real-world and simulated data sets show that M-BSRM is more effective, practical, and efficient than the other approaches.

Mobile Edge Computing is an emerging technology offering low latency responses by deploying edge servers near mobile devices. We propose a novel privacy-preserving QoS forecasting approach – Edge-Laplace QoS (QoS forecasting with Laplace noise in mobile Edge environments) to address the challenges of user mobility and information leakage encountered by QoS forecasting in mobile edge environments. Edge-Laplace QoS is able to accurately and efficiently forecast Quality of Service (QoS) of various Web Services, while effectively protecting user privacy in mobile edge environments. We employ an improved differential privacy method to add dynamic disguises to the original QoS data in the edge environment to protect user data privacy. A collaborative filtering method is adopted to retrieve similar users’ accessing records based on geographic locations of their accessed servers for QoS forecasting. We conduct a set of experiments using several public network data sets. The results show that the efficiency of Edge-Laplace QoS is superior to traditional forecasting approaches. Edge-Laplace QoS is also validated to be more suitable for edge environments than traditional privacy-preserving approaches.

Deep Neural Network (DNN) driven technologies have been extensively employed in various aspects of our life. Nevertheless, the applied DNN always fails to detect erroneous behaviors, which may lead to serious problems. Several approaches have been proposed to enhance adversarial examples for automatically testing deep learning (DL) systems, such as image-based DL systems. However, the approaches contain the following two limitations. First, existing approaches only take into account small perturbations on adversarial examples, they design and generate adversarial examples for a certain particular DNN model. This might hamper the transferability of the examples for other DNN models. Second, they only use shallow features (e.g., pixel-level features) to judge the differences between the generated adversarial examples and the original examples. The deep features, which contain high-level semantic information, such as image object categories and scene semantics, are completely neglected. To address these two problems, we proposeCAGFuzz, aCoverage-guidedAdversarialGenerativeFuzzing testing approach for image-based DL systems.CAGFuzzis able to generate adversarial examples for mainstream DNN models to discover their potential errors. First, we train an Adversarial Example Generator (AEG) based on general datasets.AEGonly considers the data characteristics to alleviate the transferability problem. Second, we extract the deep features of the original and adversarial examples, and constrain the adversarial examples by cosine similarity to ensure that the deep features of the adversarial examples remain unchanged. Finally, we use the adversarial examples to retrain the models. Based on several standard datasets, we design a set of dedicated experiments to evaluateCAGFuzz. The experimental results show thatCAGFuzzcan detect more hidden errors, enhance the accuracy of the target DNN models, and generate adversarial examples with higher transferability.

At present, most smart contract vulnerability detection use manually-defined patterns, which is time-consuming and far from satisfactory. To address this issue, researchers attempt to deploy deep learning techniques for automatic vulnerability detection in smart contracts. Nevertheless, current work mostly relies on a single code representation such as AST (Abstract Syntax Tree) or code tokens to learn vulnerability characteristics, which might lead to incompleteness of learned semantics information. In addition, the number of available vulnerability datasets is also insufficient. To address these limitations, first, we construct a dataset covering most typical types of smart contract vulnerabilities, which can accurately indicate the specific row number where a vulnerability may exist. Second, for each single code representation, we propose a novel way called AFS (AST Fuse program Slicing) to fuse code characteristic information. AFS can fuse the structured information of AST with program slicing information and detect vulnerabilities by learning new vulnerability characteristic information.

Business process specified in Business Process Execution Language (BPEL), which integrates existing services to develop composite service for offering more complicated function, is error-prone. Verification and testing are necessary to ensure the correctness of business processes. SPIN, for which the input language is PROcess MEta-LAnguage (Promela), is one of the most popular tools for detecting software defects and can be used both in verification and testing. In this paper, an automatic approach is proposed to construct the verifiable model for BPEL-based business process with Promela language. Business process is translated to an intermediate two-level representation, in which eXtended Control Flow Graph (XCFG) describes the behavior of BPEL process in the first level and Web Service Description Models (WSDM) depict the interface information of composite service and partner services in the second level. With XCFG of BPEL process, XCFGs for partner services are generated to describe their behavior. Promela model is constructed by defining data types based on WSDM and defining channels, variables and processes based on XCFGs. The constructed Promela model is closed, containing not only the BPEL process but also its execution environment. Case study shows that the proposed approach is effective.

Mobile edge computing is a new computing paradigm that performs computing on the edge of a network. It provides services to users by deploying edge servers near mobile devices. Services may be unavailable or do not satisfy the needs of users due to changing edge environments. Quality of service (QoS) is commonly employed as a critical means to indicate qualitative status of services. It is particularly important to monitor QoS of services timely and effectively in the mobile edge environment. However, user mobility and dependencies among QoS values often cause the monitoring results to deviate from the real results in the mobile edge environment. Existing QoS monitoring approaches have not taken into account these problems. To address the problems, this article proposes ghBSRM-MEC (GaussianhiddenBayeSianRuntimeMonitoring forMobileEdgeComputing), a novel mobility and dependence-aware QoS monitoring approach for the mobile edge environment. This approach assumes that the QoS attribute values of edge servers obey Gaussian distribution. It constructs a parent property for each property, thus reducing the dependence between properties. During the training stage, a Gaussian Hidden Bayesian classifier is constructed for each edge server. During the monitoring stage, combining with a KNN algorithm, the classifier is changed dynamically based on user mobility to realize QoS monitoring in the mobile edge environment. The experimental results validate the feasibility, effectiveness, and efficiency of ghBSRM-MEC.

Event logs of process-aware information systems play an increasingly critical role in today's enterprises because they are the basis for a number of business intelligence applications such as complex event processing, provenance analysis, performance analysis, and process mining. However, due to incorrect manual recording, system errors, and resource constraints, event logs inevitably contain noise in the form of deviating event sequences with redundant, missing, or dislocated events. To repair event logs, existing approaches rely on predefined process models to obtain a minimum recovery for each deviating event sequence. However, process models are typically unavailable in practice, rendering existing approaches inapplicable. In this scenario, can event logs be self-healing? To address this problem, we propose an approach that leverages compliant event sequences to repair deviating sequences. Our approach is effective if the compliant event sequences contain sufficient knowledge for repair. We implement our approach in a prototype and employ the tool to conduct experiments. The experimental results demonstrate that our approach can achieve efficient repairs without the help of process models.

We propose aLong-term Quality of Service (QoS) forecasting approach usingAdvertisement andLevenberg-Marquardt improvedRadialBasisFunction (LA-LMRBF)—a novel online QoS forecasting approach. LA-LMRBF aims to accurately predict QoS attributes of Web services in the form of multivariate time series via three stages. First, the phase space reconstruction theory is employed to restore multi-dimensional and nonlinear relations among the multivariate QoS attributes. Second, short-term QoS advertisement data is incorporated to enable long-term QoS forecasting. Finally, an optimized Radial Basis Function (RBF) neural network is constructed to forecast long-term multivariate QoS values, where the Affinity Propagation clustering algorithm is used to determine the number of hidden nodes and the Levenberg-Marquardt (LM) algorithm is utilized to dynamically update some parameters of the RBF neural network. A series of experiments are performed on a mixture of public and self-collected data sets. The results show that LA-LMRBF is superior to the other approaches and more suitable for long-term QoS forecasting.

State-of-the-art work of evaluating smart contract static analysis tools faces a major problem: most test cases (i.e., labeled buggy contracts) are too simple and lack complexity, which makes the evaluation unable to show the real performance of the analysis tools when complex contracts are analyzed. To fill the gap, we propose a novel source code obfuscation approach for Ethereum smart contracts. We use the buggy contracts in the public dataset11https://github.com/smartbugs/smartbugs/tree/master/dataset to evaluate our approach. The evaluation result shows that our approach can effectively increase the complexity of a contract. Besides, we use obfuscated contracts to evaluate the static analysis tools. The evaluation result shows that the performance of most smart contract static analysis tools decreases in different degree when the original contracts are obfuscated.

Ethereum is the largest blockchain platform that supports smart contracts. Users deploy smart contracts by publishing the smart contract's bytecode to the blockchain. Since the data in the blockchain cannot be modified, even if these contracts contain bugs, it is not possible to patch deployed smart contracts with code updates. Moreover, there is currently neither a comprehensive classification framework for Ethereum smart contract bugs, nor detailed criteria for detecting bugs in smart contracts, making it difficult for developers to fully understand the negative effects of bugs and design new approaches to detect bugs. In this paper, to fill the gap, we first collect as many smart contract bugs as possible from multiple sources and divide these bugs into 9 categories by extending the IEEE Standard Classification for Software Anomalies. Then, we design the criteria for detecting each kind of bugs, and construct a dataset of smart contracts covering all kinds of bugs. With our framework and dataset, developers can learn smart contract bugs and develop new tools to detect and locate bugs in smart contracts. Moreover, we evaluate the state-of-the-art tools for smart contract analysis with our dataset and obtain some interesting findings: 1) Mythril, Slither and Remix are the most worthwhile combination of analysis tools. 2) There are still 10 kinds of bugs that cannot be detected by any analysis tool.

This paper proposes a novel security-aware QoS (Quality of Service) forecasting approach - Edge QoS Per-PM (Edge QoS forecasting with Personalized training based on Public Models in mobile edge computing) by migrating the principle of integrating cooperative learning and independent learning from federated learning. Edge QoS Per-PM can make fast and accurate forecasting on the premise of ensuring enhanced security. We train private model based on public model for personalized forecasting. The private models are invisible to other users to ensure the absolute security. At regular intervals, a Long Short-Term Memory (LSTM) model is trained based on the latest private data to meet the realtime requirements of the dynamic edge environment and ensure the accuracy of prediction results. A series of experiments is conducted based on public network data sets. The results demonstrate that Edge QoS Per-PM can train appropriate models and achieve faster convergence and higher accuracy.

Mobile edge computing transfers computing and storage from traditional cloud servers to edge servers, presenting new challenges to quality assurance of edge services. Quality of Service (QoS) is considered as a defacto standard to evaluate similar services with different quality. Given the fact that QoS values are highly dynamic in complex edge environments, QoS monitoring is viewed as a promising technique to comprehensively and effectively understand QoS status of edge services. Due to the distributed storage of historical QoS data and the changeable edge environments, traditional QoS monitoring approaches cannot be directly applied into mobile edge computing. To address this problem, this paper proposes a novel multivariate QoS monitoring approach, called Rs-mBSRM (multivariate BayeSian Runtime Monitoring using Rough set), First, the weights of different QoS attributes are quantified and obtained according to the historical samples based on rough set theory. Second, a Bayesian classifier is constructed for each corresponding edge server during the training stage. Finally, during the monitoring stage, considering the distributed data storage, the classifier is dynamically switched and the attribute weights are also updated due to user mobility. Our experimental results on public data sets show that Rs-mBSRM is better than existing QoS monitoring approaches and is more suitable for mobile edge computing.

Rainfall forecasting is crucial in the field of meteorology and hydrology. However, existing solutions always achieve low prediction accuracy for short-term rainfall forecasting. Atmospheric forecasting models perform worse in many conditions. Machine learning approaches neglect the influences of physical factors in upstream or downstream regions, which make forecasting accuracy fluctuate in different areas. To improve the overall forecasting accuracy for short-term rainfall, this paper proposes a novel solution called Dynamic Regional Combined short-term rainfall Forecasting approach (DRCF) using Multi-layer Perceptron (MLP). First, Principal Component Analysis (PCA) is used to reduce the dimension of thirteen physical factors, which serves as the input of MLP. Second, a greedy algorithm is applied to determine the structure of MLP. The surrounding sites are perceived based on the forecasting site. Finally, to solve the clutter interference which is caused by the extension of the perception range, DRCF is enhanced with several dynamic strategies. Experiments are conducted on data from 56 real-world meteorology sites in China, and we compare DRCF with atmospheric models and other machine learning approaches. The experimental results show that DRCF outperforms existing approaches in both threat score (TS) and root mean square error (RMSE).

Precise precipitation forecast can better reflect the changing trend of climate, provide timely and efficient environmental information for management decision, as well as help people to make preparations for the incoming floods or droughts. However, existing approaches have limited ability to fore cast future precipitation in different regions. In order to addess the problem, this paper proposes a big data based approach for precipitation forecasting based on deep belief nets, called DBNPF (Deep Belief Network for Precipitation Forecast). The proposed approach can not only learn the hierarchical representation of raw data using a highly generalized way, but also make a more accurate description of the rule underlying different kind of environmental factors. A set of dedicated experiments with hydrological multivariate time series from four typical areas of China is conducted to validate the feasibility and robustness of the model. In the experiments, environmental factors, filtered by factor analysis, are used as input vector, and the next 24 hours precipitation is used as the output vector. We compare DBNPF with other traditional machine learning approaches. The experimental results show that the proposed approach is more robust than other approaches and can also improve the forecast precision.

Advancements in mobile, cloud computing and other techniques have made the world even smaller and connected like never before. It has become a challenge and an opportunity for cities to leverage these growing technologies to solve real city administration problems. Cities are in the transformation to become state-of-the-art smart cities using these technologies. This paper is about the automation of street cleanliness assessment in near real-time. It answers the question of how can we assess the status of streets in a more efficient and effective way. To address the problem, this paper proposes a multi-level assessment system on how the cleanliness status of streets is collected using mobile stations. They are connected via city network, analyzed in the cloud and presented to city administrators online or on mobile. The real case studies show the usability and feasibility of our system. This also gives opportunities for city residents to participate and contribute to making the city a better place.

With the wide-spread usage of Android systems, Android applications have become the target of mobile malwares. Therefore, an effective verification approach for Android applications is essential. Runtime verification based on monitors is one of the most promising techniques to check the software’s behaviors. Currently, there are a number of monitoring approaches for Android applications. However, these approaches mainly have two limitations. First, there is no effective mechanism to reduce the load on Android applications caused by monitors. Second, these approaches mainly rely on logic-based specifications, which are complex and not intuitive for being used in practice. In order to address these two limitations, this paper proposes a scenario-based runtime verification approach for Android applications (called Android-SRV). The approach concentrates on providing a dynamic and usable solution for monitoring applications during execution with the help of aspect-oriented programming. It will translate the scenario-based specification (called property sequence charts (PSCs)) into multi-valued automata (MAs), and then generate AspectJ codes from the MA. Finally, these AspectJ codes are weaved into the target system as monitors. Considering the impact of the monitors on performance load in the Android system, the paper proposes local and cloud collaboration mechanisms to reduce the impact. The scenario-based specification is more intuitive than the traditional logic-based specifications. The approach is shown to be an effective means for monitoring Android applications with controlled overload.

How to assure Quality of Service (QoS) of the third-party services is very important for the SOA. Effective monitoring technique towards QoS, which is an important measurement for third-party service quality, is necessary to ensure quality of Web service. Current monitoring approaches do not consider the influences of environment factors such as the position of server, user usage, and the load at runtime. Ignoring these influences, which do exist among the monitoring process, may cause existing monitoring approaches producing unpredictable monitoring results. In order to overcome this limitation, this paper proposes a novel Web Service QoS (WS-Qos) monitoring approach sensitive to environmental factors called weighted Bayesian Runtime Monitor (wBSRM) based on weighted naïve Bayesian classifiers and Term Frequency-Inverse Document Frequency (TF-IDF) algorithm. wBSRM constructs weighted naïve Bayesian classifier by learning a part of samples to classify the monitoring results. The results meeting QoS standard are classified as [Formula: see text] and the one that does not meet is classified as [Formula: see text]. Classifier can also output ratio between posterior probability of [Formula: see text] and [Formula: see text], and consequently the analysis can lead to three monitoring results including [Formula: see text], [Formula: see text] or inconclusive. A set of dedicated experiments are conducted to validate wBSRM. The experiments are based on a public dataset and a simulated dataset under the given standard. The experimental results demonstrate that wBSRM is better than previous approaches.

In order to accurately forecast Quality of Service (QoS) of different Web Services, this paper proposes a novel QoS forecasting approach called MulA-LMRBF (Multi-step fore-casting with Advertisement and Levenberg-Marquardt improved Radial Basis Function) based on multivariate time series. Considering the correlation among different QoS attributes, we use phase-space reconstruction to map historical multivariate QoS data into a dynamic system, use Average Dimension (AD) to estimate the embedding dimension and delay time of reconstructed phase space. We also add the short-term QoS advertisement data of service provider to form a more comprehensive data set. Then, RBF (Radial Basis Function) neural network improved by the Levenberg-Marquardt (LM) algorithm is used to update the weight of the neural network dynamically, which improves the forecasting accuracy and realizes the dynamic multiple-step forecasting. The experimental results demonstrate that MulA-LMRBF is better than previous approaches in term of precision and is more suitable for multi-step forecasting.

The aligning of event logs with process models is of great significance for process mining to enable conformance checking, process enhancement, performance analysis, and trace repairing. Since process models are increasingly complex and event logs may deviate from process models by exhibiting redundant, missing, and dislocated events, it is challenging to determine the optimal alignment for each event sequence in the log, as this problem is NP-hard. Existing approaches utilize the cost-based A* algorithm to address this problem. However, scalability is often not considered, which is especially important when dealing with industrial-sized problems. In this paper, by taking advantage of the structural and behavioral features of process models, we present an efficient approach which leverages effective heuristics and trace replaying to significantly reduce the overall search space for seeking the optimal alignment. We employ real-world business processes and their traces to evaluate the proposed approach. Experimental results demonstrate that our approach works well in most cases, and that it outperforms the state-of-the-art approach by up to 5 orders of magnitude in runtime efficiency.

While event logs generated by business processes play an increasingly significant role in business analysis, the quality of data remains a serious problem. Automatic recovery of dirty event logs is desirable and thus receives more attention. However, existing methods only focus on missing event recovery, or fall short of efficiency. To this end, we present Effa, a ProM plugin, to automatically recover event logs in the light of process specifications. Based on advanced heuristics including process decomposition and trace replaying to search the minimum recovery, Effa achieves a balance between repairing accuracy and efficiency.

Event logs are of paramount significance for process mining and complex event processing. Yet, the quality of event logs remains a serious problem. Missing events of logs are usually caused by omitting manual recording, system failures, and hybrid storage of executions of different processes. It has been proved that the problem of minimum recovery based on a priori process specification is NP-hard. State-of-the-art approach is still lacking in efficiency because of the large search space. To address this issue, in this paper, we leverage the technique of process decomposition and present heuristics to efficiently prune the unqualified sub-processes that fail to generate the minimum recovery. We employ real-world processes and their incomplete sequences to evaluate our heuristic approach. The experimental results demonstrate that our approach achieves high accuracy as the state-of-the-art approach does, but it is more efficient.

The quality of service-oriented system relies heavily on the third-party service. Such reliance would result in many uncertainties, in consideration of the complex and changeable network environment. Hence, effective runtime monitoring technique is required by service-oriented system. Several monitoring approaches have been proposed. However, all of these approaches do not consider the influences of environmental factors such as the position of server and users, and the load at runtime. Ignoring these influences, which exist among monitoring process, may cause wrong monitoring results. In order to solve this problem, this paper proposes a novel QoS monitoring approach sensitive to environmental factors called wBSRM (weighted Bayesian Runtime Monitoring) based on weighted naive Bayesian and TF-IDF (Term Frequency-Inverse Document Frequency). The proposed approach measures influence of environmental factor by TF-IDF algorithm and then constructs weighted naïve Bayesian classifier by learning part of samples to classify monitoring results. Experiments are conducted based on both public network data set and randomly generated data set. The experimental results demonstrate that our approach is better than previous approaches.

The paper proposes a novel approach based on the hierarchical timed automata to verify the consistency of dynamic evolution process. Different from traditional approaches, it investigates the problem from the behavioral perspective and examines the procedures before, during and after the evolution process. Furthermore, our approach can support the direct modeling of temporal aspects, as well as the hierarchical structures. A flattening algorithm is presented to facilitate the automated verification using the mainstream timed automata based model checker --UPPAAL. A motivating example is discussed and demonstrates the feasibility of our approach.

Aiming at optimizing Web service composition which satisfies user's multiple QoS constraints, an efficient graph-based Web service composition approach, named Skyline improved Multi Constraint Shortest Path-Relax (Sky-MCSP-R), is proposed. Firstly, the approach selects Skyline services from candidate service spaces, thus it can construct the model of Web service composition directly on these high quality candidate services, reducing the whole number of nodes of the model. Secondly, the approach uses MCSP-K algorithm which uses over constraint mechanism to compose basic services, and reduces the constraint intensity so to make algorithm MCSP-K produce as many feasible solutions as possible. Thirdly, the approach uses Relax algorithm to optimize the solutions. Experimental results show that the approach improves the efficiency of Web service composition and keeps a high optimization rate, reducing no solution phenomenons. The results also indicate that our approach is superior to previous approaches.

Run-time verification techniques based on monitors have become the basic means of detecting software failures in dynamic and open environments. One challenging problem is how the monitor can provide sufficient indications before the real failures, so that the system has enough time to act before the failures cause serious harm. To this end, this paper proposes the main idea on how to generate monitors from a scenario-based specification called property sequence chart based on game theory. The monitors are interpreted in multivalued semantics: satisfied, infinitely controllable, system finitely controllable, system urgently controllable, environment finitely controllable, environment urgently controllable, violated. Through the multi-valued semantics definition, the monitors can provide enough information to help the system to take measures for failure prevention or recovery.

Web service composition is a new paradigm to develop distributed and reactive software-intensive systems. Predicting and preventing failures of dynamic composite services is an important and challenge problem due to the dynamically evolving attribute. In previous work, we propose CASSANDRA, a novel proactive monitoring technique with the ability to predict and prevent the potential failures happening in dynamic evolvable system. In this paper, we concretize the approach into web service composition field. By combining runtime information and design-time specification of basic services, the approach can analyse future -step models ahead of the current service execution states. Then, this model can be used to check with a set of desired properties represented by property sequence chart. Initial experiments on an online medicine case study validates our approach and shows encouraging results.

The scenario-based specifications are popularly used to capture user requirements. The state-based specifications are very appropriate to capture system design. Recently, there has been increased research interest in connecting these two kinds of specifications, called synthesis. Synthesis is a way to automatically construct the state-based specifications from the scenario-based specifications. There are two kinds of synthesis methods: global synthesis and local synthesis. Global synthesis means constructing a state-based specification for the whole system from the scenario-based specifications, while local synthesis means constructing a state-based specification for each object in the system. The two different synthesis methods have different uses and need to be systematically compared. The contributions of this paper are twofold. Firstly, we propose an improved method supporting the global and the local synthesis of state machines (a kind of state-based specifications) by using a novel algorithm for state machine execution and an algorithm similar to operator priority analysis method, which can fully automate the process of synthesis. Our synthesis method also satisfies two important properties: completeness and soundness. Secondly, to the best of our knowledge, our work does the first attempt to systematically compare global synthesis with local synthesis, and shows some insightful results of the experimental comparison between the two kinds of synthesis methods, which are valuable for the practitioners to choose an appropriate synthesis method for the analysis and verification of the system.

In run-time evolving systems, components may evolve while the system is being operated. Unsafe run-time changes may compromise the correct execution of the entire system. Traditional design-time verification techniques difficultly cope with run-time changes, and run-time monitoring may detect disfunctions only too late, when the failure arises. The desire would be to define advanced monitors with the ability to predict and prevent the potential errors happening in the future. In this direction, this paper proposes CASSANDRA, a new approach that by combining design-time and run-time analysis techniques, can “look ahead” in the near execution future, and predict potential failures. During run-time we on-the-fly construct a model of the future k-step global state space according to design-time specifications and the current execution state. Consequently, we can run-time check whether possible failures might happen in the future.

Abstract Run‐time monitoring is an important technique to detect erroneous run‐time behaviors. Several techniques have been proposed to automatically generate monitors from specification languages to check temporal and real‐time properties. However, monitoring of probabilistic properties still requires manual generation. To overcome this problem, we define a formal property specification language called Probabilistic Timed Property Sequence Chart (PTPSC). PTPSC is a probabilistic and timed extension of the existing scenario‐based specification formalism Property Sequence Chart (PSC). We have defined a formal grammar‐based syntax and have implemented a syntax‐directed translator that can automatically generate a probabilistic monitor which combines timed B”uchi automata and a sequential statistical hypothesis test process. We validate the generated monitors with a set of experiments performed with our tool WS‐PSC Monitor. Copyright © 2011 John Wiley & Sons, Ltd.

The Web Services Choreography Description Language (WS-CDL) is a specification developed by the W3C and can be viewed as a blueprint for the development of end-point services. Consequently, it is worth providing a systematic approach for its modeling, analysis and verification. The Unified Modeling Language (UML) is an industry standard for modeling. Applying UML to model WS-CDL is obviously a promising solution to bring together academics and practitioners through a unique standard language. In this paper, we propose to use different UML diagrams to model WS-CDL. UML Component Diagram is used to model the underlying structure of WS-CDL. UML Sequence Diagram is utilized to model the activities in WS-CDL. UML State Machine Diagram is utilized to model the behaviors of each role participating in a WS-CDL specification. We then enrich the UML State Machine Diagram with data by the use of UML Class Diagram. Given the UML specification of WS-CDL, we then provide a systematic way of formally analyzing and verifying WS-CDL against desired properties. Some experiments show that our approach can verify structural, behavioral and data properties in a middle-scale data-enriched WS-CDL specification.

Probabilistic properties are considered as the most important requirements for a variety of software systems, since they are used to formulate extra-functional requirements such as reliability, availability, safety, security and performance requirements. Currently, several probabilistic logics have been proposed to specify such important properties. However, due to the inherent complexity of the underlying temporal logics, these probabilistic logics are rather complex and software developers have problems using them to correctly specify the intended properties. To overcome this problem, we define a formal and graphical property specification language called probabilistic timed property sequence charts (PTPSC) which is a probabilistic extension of property sequence charts (PSC). We illustrate the use of PTPSC in the context of a vehicle-to-vehicle communication device for avoiding traffic accidents.

Monitoring allows for checking if a system fulfils its requirements at runtime. This is required for quality assurance purposes. Currently several approaches exist to monitor standard and timing properties. However, a current challenge is to provide a comprehensive approach for monitoring probabilistic properties, as they are used to formulate performance, reliability, safety, and availability requirements. The main problem of these probabilistic properties is that there is no binary acceptance condition. To overcome this problem, this paper describes a monitoring approach called ProMo that is based on acceptance sampling and sequential hypothesis testing. This approach is validated based on several experiments that have been performed on an example system which provides medical assistance in remote areas.

Due to the dynamically evolving attribute, validation of composite services must be extended from design time to run-time. Dynamical verification techniques, such as runtime monitoring, have been first class activities to be performed during the execution of composite services. For a kind of composite services, nonfunctional properties, such as timed properties, are as important as functional properties and need to be monitored at run-time. However, using traditional logic and formalism, these timed properties are not easily represented for general software engineers. In order to deal with this problem, we first extend a novel notation (Property Sequence Chart) with time constructs. Then, we give its semantics in terms of timed Buchi automata and measure its expressiveness based on recently proposed real-time specification patterns. Finally, we propose a novel framework to monitor two kinds of timed properties in composite services: the accomplished time of basic service operations and some additional timed assumptions of the composition process. Our framework provides a completely graphical front-end which can friendly help general software engineers to monitor the timed properties in composite services.

Runtime monitoring is significantly essential for web service compositions. For a kind of composite services, nonfunctional properties, such as timed properties, are as important as functional properties and need to be monitored in runtime. In this paper, we extend properly sequence chart into timed properly sequence chart and propose a new approach to monitor two kinds of timed properties in web service compositions: the accomplished time of basic service operations and some additional timed assumptions of the composition process. Our approach is more intuitive than traditional monitoring approaches.

The Web Services Choreography Description Language (WS-CDL) is a specification developed by the W3C that can be viewed as a blueprint for the development of end-point services. Considering that it is the W3C candidate recommendation for web service choreography, it is worth providing a systematic approach for its modeling, analysis and verification. The Unified Modeling Language (UML) is the de facto industry standard for modeling. Applying UML to model WS-CDL is obviously a promising solution to bring together academics and practitioners in through a unique standard language. This paper proposes to use different UML diagrams to model WS-CDL. Given the UML specification of WS-CDL, we then provide a systematic way of formally analyzing and verifying WS-CDL.