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Scheduling transactions in mobile distributed real-time database systems 被引量:1
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作者 雷向东 赵跃龙 +1 位作者 陈松乔 袁晓莉 《Journal of Central South University of Technology》 EI 2008年第4期545-551,共7页
A DMVOCC-MVDA (distributed multiversion optimistic concurrency control with multiversion dynamic adjustment) protocol was presented to process mobile distributed real-time transaction in mobile broadcast environment... A DMVOCC-MVDA (distributed multiversion optimistic concurrency control with multiversion dynamic adjustment) protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load (think time is ls) the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols. 展开更多
关键词 mobile distributed real-time database systems muliversion optimistic concurrency control multiversion dynamic adjustment pre-validation multiversion data broadcast
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Quasi Serializable Concurrency Control in Distributed Real-Time Database Systems
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作者 党德鹏 Liu Yunsheng 《High Technology Letters》 EI CAS 2003年第1期72-76,共5页
This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, thro... This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, through a series of simulation studies, it shows that using the new concurrency control protocol the performance of distributed real-time databases can be much improved. 展开更多
关键词 distributed real-time database systems relaxing serializability real-tirne concurrency control
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Validation concurrency control protocol in parallel real-time database systems 被引量:3
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作者 LEI Xiang-dong(雷向东) YUAN Xiao-li(袁晓莉) 《Journal of Central South University of Technology》 2002年第3期197-201,共5页
In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can e... In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold. 展开更多
关键词 PARALLEL database system real-time database CONCURRENCY control VALIDATION TRANSACTIONS
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A dynamic crash recovery scheme for distributed real-time database systems
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作者 肖迎元 刘云生 +2 位作者 刘小峰 廖国琼 王洪亚 《Journal of Shanghai University(English Edition)》 CAS 2006年第6期510-516,共7页
Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme (TCLCRS) that aims at distributed ... Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme (TCLCRS) that aims at distributed real-time databases, which adopts a main memory database as its ground support. In our scheme, each site maintains a real-time log for local transactions and the subtransactions, which execute at the site, and execte local checkpointing independently. Log records are stored in non-volatile high- speed store, which is divided into four different partitions based on transaction classes. During restart recovery after a site crash, partitioned crash recovery strategy is adopted to ensure that the site can be brought up before the entire local secondary database is reloaded in main memory. The partitioned crash recovery strategy not only guarantees the internal consistency to be recovered, but also guarantee the temporal consistency and recovery of the sates of physical world influenced by uncommitted transactions. Combined with two- phase commit protocol, TCLCRS can guarantee failure atomicity of distributed real-time transactions. 展开更多
关键词 distributed real-time database system partitioned real-time logging partitioned crash recovery.
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Weak Serializable Concurrency Control in Distributed Real-Time Database Systems
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作者 党德鹏 刘云生 潘琳 《Journal of Shanghai University(English Edition)》 CAS 2002年第4期325-330,共6页
Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of sa... Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of satisfying the timing constraints of transactions, serializability is too strong as a correctness criterion and not suitable for real time databases in most cases. On the other hand, relaxed serializability including epsilon serializability and similarity serializability can allow more real time transactions to satisfy their timing constraints, but database consistency may be sacrificed to some extent. We thus propose the use of weak serializability(WSR) that is more relaxed than conflicting serializability while database consistency is maintained. In this paper, we first formally define the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol WDHP(weak serializable distributed high priority protocol) is outlined for distributed real time databases, where a new lock mode called mask lock mode is proposed for simplifying the condition of global consistency. Finally, through a series of simulation studies, it is shown that using the new concurrency control protocol the performance of distributed real time databases can be greatly improved. 展开更多
关键词 distributed real time database systems relaxed serializability real time concurrency control read only transactions.
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Classification of Cybersecurity Threats, Vulnerabilities and Countermeasures in Database Systems
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作者 Mohammed Amin Almaiah Leen Mohammad Saqr +3 位作者 Leen Ahmad Al-Rawwash Layan Ahmed Altellawi Romel Al-Ali Omar Almomani 《Computers, Materials & Continua》 SCIE EI 2024年第11期3189-3220,共32页
Database systems have consistently been prime targets for cyber-attacks and threats due to the critical nature of the data they store.Despite the increasing reliance on database management systems,this field continues... Database systems have consistently been prime targets for cyber-attacks and threats due to the critical nature of the data they store.Despite the increasing reliance on database management systems,this field continues to face numerous cyber-attacks.Database management systems serve as the foundation of any information system or application.Any cyber-attack can result in significant damage to the database system and loss of sensitive data.Consequently,cyber risk classifications and assessments play a crucial role in risk management and establish an essential framework for identifying and responding to cyber threats.Risk assessment aids in understanding the impact of cyber threats and developing appropriate security controls to mitigate risks.The primary objective of this study is to conduct a comprehensive analysis of cyber risks in database management systems,including classifying threats,vulnerabilities,impacts,and countermeasures.This classification helps to identify suitable security controls to mitigate cyber risks for each type of threat.Additionally,this research aims to explore technical countermeasures to protect database systems from cyber threats.This study employs the content analysis method to collect,analyze,and classify data in terms of types of threats,vulnerabilities,and countermeasures.The results indicate that SQL injection attacks and Denial of Service(DoS)attacks were the most prevalent technical threats in database systems,each accounting for 9%of incidents.Vulnerable audit trails,intrusion attempts,and ransomware attacks were classified as the second level of technical threats in database systems,comprising 7%and 5%of incidents,respectively.Furthermore,the findings reveal that insider threats were the most common non-technical threats in database systems,accounting for 5%of incidents.Moreover,the results indicate that weak authentication,unpatched databases,weak audit trails,and multiple usage of an account were the most common technical vulnerabilities in database systems,each accounting for 9%of vulnerabilities.Additionally,software bugs,insecure coding practices,weak security controls,insecure networks,password misuse,weak encryption practices,and weak data masking were classified as the second level of security vulnerabilities in database systems,each accounting for 4%of vulnerabilities.The findings from this work can assist organizations in understanding the types of cyber threats and developing robust strategies against cyber-attacks. 展开更多
关键词 Cyber threats database systems cyber risk assessment VULNERABILITIES COUNTERMEASURES
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The Multi-level Recovery of Main-memory Real-time Database Systems with ECBH
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作者 ZOU Yong-gui, GE Jun-wei (College of Computer Science and Technology, Chonqqing University of Posts and Telecommunications, Chongqing 400065, P.R. China) 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2003年第1期15-24,共10页
Storing the whole database in the main-memory is a common method to processreal-time transaction in real-time database systems. The recovery mechanism of Main-memory Real-timeDatabase Systems (MMRTDBS) should reflect ... Storing the whole database in the main-memory is a common method to processreal-time transaction in real-time database systems. The recovery mechanism of Main-memory Real-timeDatabase Systems (MMRTDBS) should reflect the characteristics of the main-memory database andreal-time database because their structures are quite different from other conventional databasesystems. In this paper, therefore, we propose a multi-level recovery mechanism for main-memoryreal-time database systems with Extendable Chained Bucket Hashing (ECBH). Owing to the occurrence ofreal-time data in real-time systems, we should also consider it in our recovery mechanism .According to our performance test, this mechanism can improve the transaction concurrency, reducingtransactions ' deadline missing rate. 展开更多
关键词 DBMS multi-level recovery HASH main- memory database real-time
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Multimedia Engineering Database Management Systems
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作者 梁允荣 郭贵锁 +3 位作者 宋瀚涛 冯希 高春雷 郭胜 《Journal of Beijing Institute of Technology》 EI CAS 1996年第1期68-73,共6页
In the Engine CAD application system engineering database management system (ECAD-EDBMS) is the kernel. ECAD-EDBMS can manage and process the multimedia such as graphics, data, text, sound, image and video. It provide... In the Engine CAD application system engineering database management system (ECAD-EDBMS) is the kernel. ECAD-EDBMS can manage and process the multimedia such as graphics, data, text, sound, image and video. It provides the integrated environment and more functions for many subsystems of ECAD and engine designers. So it improves the design efficiency. 展开更多
关键词 database management systems multimedia technology engineering CAD
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Cyber Resilience through Real-Time Threat Analysis in Information Security
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作者 Aparna Gadhi Ragha Madhavi Gondu +1 位作者 Hitendra Chaudhary Olatunde Abiona 《International Journal of Communications, Network and System Sciences》 2024年第4期51-67,共17页
This paper examines how cybersecurity is developing and how it relates to more conventional information security. Although information security and cyber security are sometimes used synonymously, this study contends t... This paper examines how cybersecurity is developing and how it relates to more conventional information security. Although information security and cyber security are sometimes used synonymously, this study contends that they are not the same. The concept of cyber security is explored, which goes beyond protecting information resources to include a wider variety of assets, including people [1]. Protecting information assets is the main goal of traditional information security, with consideration to the human element and how people fit into the security process. On the other hand, cyber security adds a new level of complexity, as people might unintentionally contribute to or become targets of cyberattacks. This aspect presents moral questions since it is becoming more widely accepted that society has a duty to protect weaker members of society, including children [1]. The study emphasizes how important cyber security is on a larger scale, with many countries creating plans and laws to counteract cyberattacks. Nevertheless, a lot of these sources frequently neglect to define the differences or the relationship between information security and cyber security [1]. The paper focus on differentiating between cybersecurity and information security on a larger scale. The study also highlights other areas of cybersecurity which includes defending people, social norms, and vital infrastructure from threats that arise from online in addition to information and technology protection. It contends that ethical issues and the human factor are becoming more and more important in protecting assets in the digital age, and that cyber security is a paradigm shift in this regard [1]. 展开更多
关键词 Cybersecurity Information Security Network Security Cyber Resilience real-time Threat Analysis Cyber Threats Cyberattacks Threat Intelligence Machine Learning Artificial Intelligence Threat Detection Threat Mitigation Risk Assessment Vulnerability Management Incident Response Security Orchestration Automation Threat Landscape Cyber-Physical systems Critical Infrastructure Data Protection Privacy Compliance Regulations Policy Ethics CYBERCRIME Threat Actors Threat Modeling Security Architecture
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An Efficient Real-Time Fault-Tolerant Scheduling Algorithm Based on Multiprocessor Systems 被引量:6
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作者 YANG Fumin LUO Wei PANG Liping 《Wuhan University Journal of Natural Sciences》 CAS 2007年第1期113-116,共4页
In the context of real-time fault-tolerant scheduling in multiprocessor systems, Primary-backup scheme plays an important role. A backup copy is always preferred to be executed as passive backup copy whenever possible... In the context of real-time fault-tolerant scheduling in multiprocessor systems, Primary-backup scheme plays an important role. A backup copy is always preferred to be executed as passive backup copy whenever possible because it can take the advantages of backup copy de-allocation technique and overloading technique to improve schedulability. In this paper, we propose a novel efficient fault-tolerant ratemonotonic best-fit algorithm efficient fault-tolerant rate-monotonic best-fit (ERMBF) based on multiprocessors systems to enhance the schedulability. Unlike existing scheduling algorithms that start scheduling tasks with only one processor. ERMBF pre-allocates a certain amount of processors before starting scheduling tasks, which enlarge the searching spaces for tasks. Besides, when a new processor is allocated, we reassign the task copies that have already been assigned to the existing processors in order to find a superior tasks assignment configuration. These two strategies are all aiming at making as many backup copies as possible to be executed as passive status. As a result, ERMBF can use fewer processors to schedule a set of tasks without losing real-time and fault-tolerant capabilities of the system. Simulation results reveal that ERMBF significantly improves the schedulability over existing, comparable algorithms in literature. 展开更多
关键词 real-time periodic tasks FAULT-TOLERANCE primary/backup copy multiprocessor systems
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An Efficient Crash Recovery Technique for Real-Time Main Memory Database 被引量:3
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作者 XIAOYing-yuan LIUYun-sheng LIAOGuo-qiong LIANGPing 《Wuhan University Journal of Natural Sciences》 CAS 2005年第1期61-64,共4页
This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on t... This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on transaction types. Similarly, a main memory database isdivided into four partitions based data types. When the using ratio of log store area exceeds thethreshold value, checkpoint procedure is triggered. During executing checkpoint procedure, someuseless log records are deleted. During restart recovery after a crash, partition reloading policyis adopted to assure that critical data are reloaded and restored in advance, so that the databasesystem can be brought up before the entire database is reloaded into main memory. Therefore downtime is obvionsly reduced. Simulation experiments show our recovery scheme obviously improves thesystem performance, and does a favor to meet the dtadlints of real-time transactions. 展开更多
关键词 real-time main memory database crash recovery log scheme
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Use of Dynamical Systems Modeling to Hybrid Cloud Database 被引量:1
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作者 Evgeniy V. Pluzhnik Evgeny V. Nikulchev 《International Journal of Communications, Network and System Sciences》 2013年第12期505-512,共8页
In the article, an experiment is aimed at clarifying the transfer efficiency of the database in the cloud infrastructure. The system was added to the control unit, which has guided the database search in the local par... In the article, an experiment is aimed at clarifying the transfer efficiency of the database in the cloud infrastructure. The system was added to the control unit, which has guided the database search in the local part or in the cloud. It is shown that the time data acquisition remains unchanged as a result of modification. Suggestions have been made about the use of the theory of dynamic systems to hybrid cloud database. The present work is aimed at attracting the attention of specialists in the field of cloud database to the apparatus control theory. The experiment presented in this article allows the use of the description of the known methods for solving important practical problems. 展开更多
关键词 Hybrid CLOUD database CLOUD COMPUTING Time of QUERY DYNAMICAL systems Control THEORY
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A BiLSTM cardinality estimator in complex database systems based on attention mechanism 被引量:1
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作者 Qiang Zhou Guoping Yang +6 位作者 Haiquan Song Jin Guo Yadong Zhang Shengjie Wei Lulu Qu Louis Alberto Gutierrez Shaojie Qiao 《CAAI Transactions on Intelligence Technology》 SCIE EI 2022年第3期537-546,共10页
An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are in... An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are inaccurate and the query efficiency cannot be guaranteed as well.In particular,they are difficult to accurately obtain the complex relationships between multiple tables in complex database systems.When dealing with complex queries,the existing cardinality estimators cannot achieve good results.In this study,a novel cardinality estimator is proposed.It uses the core techniques with the BiLSTM network structure and adds the attention mechanism.First,the columns involved in the query statements in the training set are sampled and compressed into bitmaps.Then,the Word2vec model is used to embed the word vectors about the query statements.Finally,the BiLSTM network and attention mechanism are employed to deal with word vectors.The proposed model takes into consideration not only the correlation between tables but also the processing of complex predicates.Extensive experiments and the evaluation of BiLSTM-Attention Cardinality Estimator(BACE)on the IMDB datasets are conducted.The results show that the deep learning model can significantly improve the quality of cardinality estimation,which is a vital role in query optimisation for complex databases. 展开更多
关键词 ATTENTION BiLSTM cardinality estimation complex database systems query optimiser Word2vec
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A State-of-the-Art Survey on Real-Time Issues in Embedded Systems Virtualization 被引量:1
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作者 Zonghua Gu Qingling Zhao 《Journal of Software Engineering and Applications》 2012年第4期277-290,共14页
Virtualization has gained great acceptance in the server and cloud computing arena. In recent years, it has also been widely applied to real-time embedded systems with stringent timing constraints. We present a compre... Virtualization has gained great acceptance in the server and cloud computing arena. In recent years, it has also been widely applied to real-time embedded systems with stringent timing constraints. We present a comprehensive survey on real-time issues in virtualization for embedded systems, covering popular virtualization systems including KVM, Xen, L4 and others. 展开更多
关键词 VIRTUALIZATION Embedded systems real-time SCHEDULING
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THE OPTIMAL TRUNCATED LOW-DIMENSIONAL DYNAMICAL SYSTEMS BASED ON FLOW DATABASES 被引量:3
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作者 吴锤结 史汉生 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1996年第2期104-116,共13页
A new theory on the construction of optimal truncated Low-Dimensional Dynamical Systems (LDDSs) with different physical meanings has been developed, The physical properties of the optimal bases are reflected in the us... A new theory on the construction of optimal truncated Low-Dimensional Dynamical Systems (LDDSs) with different physical meanings has been developed, The physical properties of the optimal bases are reflected in the user-defined optimal conditions, Through the analysis of linear and nonlinear examples, it is shown that the LDDSs constructed by using the Proper Orthogonal Decomposition (POD) method are not the optimum. After comparing the errors of LDDSs based on the new theory POD and Fourier methods, it is concluded that the LDDSs based on the new theory are optimally truncated and catch the desired physical properties of the systems. 展开更多
关键词 partial differential equation flow database optimization dynamical system
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Partitioned k-Exclusion Real-Time Locking Protocol Motivated by Multicore Multi-GPU Systems
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作者 Mao-Lin Yang Hang Lei +1 位作者 Yong Liao Ze-Wei Chen 《Journal of Electronic Science and Technology》 CAS CSCD 2016年第3期193-198,共6页
Graphic processing units (GPUs) have been widely recognized as cost-efficient co-processors with acceptable size, weight, and power consumption. However, adopting GPUs in real-time systems is still challenging, due ... Graphic processing units (GPUs) have been widely recognized as cost-efficient co-processors with acceptable size, weight, and power consumption. However, adopting GPUs in real-time systems is still challenging, due to the lack in framework for real-time analysis. In order to guarantee real-time requirements while maintaining system utilization ~in modern heterogeneous systems, such as multicore multi-GPU systems, a novel suspension-based k-exclusion real-time locking protocol and the associated suspension-aware schedulability analysis are proposed. The proposed protocol provides a synchronization framework that enables multiple GPUs to be efficiently integrated in multicore real-time systems. Comparative evaluations show that the proposed methods improve upon the existing work in terms of schedulability. 展开更多
关键词 Embedded systems graphic processing units(GPUs) heterogeneous systems locking protocols MULTICORE real-time systems
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An OWL-Based Specification of Database Management Systems
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作者 Sabin C.Buraga Daniel Amariei Octavian Dospinescu 《Computers, Materials & Continua》 SCIE EI 2022年第3期5537-5550,共14页
In the context of a proliferation of DatabaseManagement Systems(DBMSs),we have envisioned and produced an OWL 2 ontology able to provide a high-level machine-processable description of the DBMSs domain.This conceptual... In the context of a proliferation of DatabaseManagement Systems(DBMSs),we have envisioned and produced an OWL 2 ontology able to provide a high-level machine-processable description of the DBMSs domain.This conceptualization aims to facilitate a proper execution of various software engineering processes and database-focused administration tasks.Also,it can be used to improve the decision-making process for determining/selecting the appropriate DBMS,subject to specific requirements.The proposed model describes the most important features and aspects regarding the DBMS domain,including the support for various paradigms(relational,graph-based,key-value,tree-like,etc.),query languages,platforms(servers),plus running environments(desktop,Web,cloud),specific contexts—i.e.,focusing on optimizing queries,redundancy,security,performance,schema vs.schema-less approaches,programming languages/paradigms,and others.The process of populating the ontology with significant individuals(actual DBMSs)benefits from the existing knowledge exposed by free and open machine-processable knowledge bases,by using structured data fromWikipedia and related sources.The pragmatic use of our ontology is demonstrated by two educational software solutions based on current practices in Web application development,proving support for learning and experimenting key features of the actual semantic Web technologies and tools.This approach is also an example of using multiple knowledge from database systems,semanticWeb technologies,and software engineering areas. 展开更多
关键词 database management systems knowledge model web engineering
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Energy-Efficient Deterministic Fault-Tolerant Scheduling for Embedded Real-Time Systems
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作者 李国徽 胡方晓 +1 位作者 杜小坤 唐向红 《Journal of Southwest Jiaotong University(English Edition)》 2009年第4期283-291,共9页
By combining fault-tolerance with power management, this paper developed a new method for aperiodic task set for the problem of task scheduling and voltage allocation in embedded real-time systems. The scbedulability ... By combining fault-tolerance with power management, this paper developed a new method for aperiodic task set for the problem of task scheduling and voltage allocation in embedded real-time systems. The scbedulability of the system was analyzed through checkpointing and the energy saving was considered via dynamic voltage and frequency scaling. Simulation results showed that the proposed algorithm had better performance compared with the existing voltage allocation techniques. The proposed technique saves 51.5% energy over FT-Only and 19.9% over FT + EC on average. Therefore, the proposed method was more appropriate for aperiodic tasks in embedded real-time systems. 展开更多
关键词 Embedded real-time systems Aperiodic tasks Fault tolerance Power management Task scheduling and voltageallocation
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T4SP: A Novel Tool and Database for Type IV Secretion Systems in Bacterial Genomes
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作者 ZHANG Wen YU Wei Wen +5 位作者 LIU Di LI Ming DU Peng Cheng WU Yi Lei George F. GAO CHEN Chen 《Biomedical and Environmental Sciences》 SCIE CAS CSCD 2013年第7期614-617,共4页
Secretion systems, macromolecules to pass which can mediate the across cellular membranes, are essential for virulent and genetic material exchange among bacterial species[1]. Type IV secretion system (T4SS) is one ... Secretion systems, macromolecules to pass which can mediate the across cellular membranes, are essential for virulent and genetic material exchange among bacterial species[1]. Type IV secretion system (T4SS) is one of the secretion systems and it usually consists of 12 genes: VirB1, VirB2 ...VirB11, and VirD4[2]. The structure and molecular mechanisms of these genes have been well analyzed in Gram-negative strains[3] and Gram-positive strains were once believed to be lack of T4SS. However, some recent studies revealed that one or more virB/D genes also exist in some kinds of Gram-positive bacteria and play similar role, and form a T4SS-like system[3]. The VirBl-like, VirB4, VirB6, and VirD4 genes were identified in the chromosome of Gram-positive bacterium Streptococcus suis in our previous studies and their role as important mobile elements for horizontal transfer to recipients in an 89 K pathogenicity island (PAl) was demonstrated[45]. However, their structure and molecular mechanisms in other strains, especially in Gram-positive strains, are remained unclear. 展开更多
关键词 T4SP A Novel Tool and database for Type IV Secretion systems in Bacterial Genomes
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Assigning Real-Time Tasks in Environmentally Powered Distributed Systems
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作者 Jian Lin Albert M. K. Cheng 《Circuits and Systems》 2014年第4期98-113,共16页
Harvesting energy for execution from the environment (e.g., solar, wind energy) has recently emerged as a feasible solution for low-cost and low-power distributed systems. When real-time responsiveness of a given appl... Harvesting energy for execution from the environment (e.g., solar, wind energy) has recently emerged as a feasible solution for low-cost and low-power distributed systems. When real-time responsiveness of a given application has to be guaranteed, the recharge rate of obtaining energy inevitably affects the task scheduling. This paper extends our previous works in?[1] [2] to explore the real-time task assignment problem on an energy-harvesting distributed system. The solution using Ant Colony Optimization (ACO) and several significant improvements are presented. Simulations compare the performance of the approaches, which demonstrate the solutions effectiveness and efficiency. 展开更多
关键词 Distributed systems Energy HARVESTING real-time SCHEDULING TASK ASSIGNMENT
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