面向细粒度源代码变更的缺陷预测方法

软件在其生命周期中不断地发生变更,以适应需求和环境的变化。为了及时预测每次变更是否引入了缺陷,研究者们提出了面向软件源代码变更的缺陷预测方法。然而现有方法存在以下3点不足：(1)仅实现了较粗粒度(事务级和源文件级变更)的预测;(2)仅采用向量空间模型表征变更,没有充分挖掘蕴藏在软件库中的程序结构、自然语言语义以及历史等信息;(3)仅探讨较短时间范围内的预测,未考虑在长时间软件演化过程中由于新需求或人员重组等外界因素所带来的概念漂移问题。针对现有的不足,提出一种面向源代码变更的缺陷预测方法。该方法将细粒度(语句级)变更作为预测对象,从而有效降低了质量保证成本;采用程序静态分析和自然语言语义主题推断相结合的技术深入挖掘软件库,从变更的上下文、内容、时间以及人员4个方面构建特征集,从而揭示了变更易于引入缺陷的因素;采用特征熵差值矩阵分析了软件演化过程中概念漂移问题的特点,并通过一种伴随概念回顾的动态窗口学习机制实现了长时间的稳定预测。通过6个著名开源软件验证了该方法的有效性。     

基于Change-Tree的本体变更日志存储研究

本体变更的目的是为了适应环境的变化,而变更的前提是要保证本体和使用它的应用或数据间的兼容性,本体概念或属性的重命名、合并、分解都可能造成本体与应用间的不兼容.提出了一种基于Change-Tree的本体变更日志存储方法.该方法采用有向树来组织本体的变更过程,用变更树节点来存储本体变更的信息,用节点间与或关系来关联本体的变更类型;同时该方法能采用树搜索来遍历本体变更的每一个历史阶段,从而为重现本体变化的历史提供了一种灵活高效的途径.     

基于数据库事务的土地利用变更事务模型研究*

通过对现行各种事务模型的分析,根据土地利用信息系统中土地利用变更的特点,结合分支汇合事务模型的思想,提出了基于数据库事务的土地利用变更事务模型,详细阐述了在此模型下变更事务的实现机制。实践证明,土地利用变更事务模型不仅确保变更后数据的一致性和完整性,而且能实现历史数据的恢复。     

基于Change Tree的本体变更日志存储研究*

本体变更的目的是为了适应环境的变化,而变更的前提是要保证本体和使用它的应用或数据间的兼容性,本体概念或属性的重命名、合并、分解都可能造成本体与应用间的不兼容。提出了一种基于ChangeTree的本体变更日志存储方法。该方法采用有向树来组织本体的变更过程,用变更树节点来存储本体变更的信息,用节点间与或关系来关联本体的变更类型;同时该方法能采用树搜索来遍历本体变更的每一个历史阶段,从而为重现本体变化的历史提供了一种灵活高效的途径。     

隐私安全策略中的变更影响分析

为了解决Web分布式系统中的隐私安全策略在制定和变更中的错误很难被发现的问题,提出了策略变更中各种情况的相应变更影响分析算法。对以可扩展访问控制标记语言(XACML)为代表的隐私安全策略语言中的变更理论进行了研究,定义了变更分析中的相关概念,通过把策略中的字符串元素转化成对应整数值建立一个优化的树形数据结构,利用树的特征分析变更后果。这使得一个管理员可以在正式应用策略变更前检验即将实施的变更是否符合自己的真正意图,从而大大增强系统安全性。最后实现了一个原型系统,并可以应用到其他标准策略语言。     

数据库恶意事务恢复日志系统

恶意事务攻击成功后的数据恢复机制要求日志文件必须同时记录写操作信息和读操作信息。为此,提出一种数据库恶意事务恢复日志策略,并基于该策略设计日志系统。在日志系统中,结构化查询语言(SQL)语句过滤可保护日志文件的安全,拒绝终端客户对日志文件的非法操作;敏感信息设置从行级和列级2个方面设置日志记录必须满足的约束条件,可有效控制日志文件的规模;写日志产生器通过使用触发器的临时表完成对写操作的记录;读日志产生器通过重构SQL语句产生临时表,再访问临时表完成对读操作的记录。实验结果表明,该系统可有效记录数据库读写操作,但同时会降低整体系统的效率。     

基于双重维度发现代码变更模式的挖掘方法

在代码演变的历史中,识别出重复的代码变更,对工具开发者、项目开发者、代码研究者都大有裨益。本文在代码演变的历史信息中,通过抽取细粒度的变更,采用两重维度划分事务,应用频繁项集挖掘算法,提取出一些频繁的代码变更模式。并以真实项目为对象进行了实验分析,结果表明该方法能有效挖掘出项目演变历史中的频繁代码变更,检测出有意义的高层次程序转换。     

自修复数据库系统日志机制研究

选择性恢复使得一个自修复数据库系统在受到恶意攻击后,只需撤销历史中受到恶意事务感染的那部分操作,无需回滚整段历史,但要求日志机制支持对事务间依赖关系的追踪及前像数据的长期保存。通过分析传统日志机制的不足以及现有原型系统实现方法存在的问题,提出了一种新的日志结构。该日志包含事务依赖信息,并以前像表代替传统日志机制中的回滚段。给出了基于该日志结构的数据库恢复方法,并在时间和空间开销方面对本方法与其它方法进行了分析和比较。     

需求变更技术债务研究

在软件生命周期中,需求不断发生变更,而需求决策往往取决于开发人员的偏好和权衡,缺乏一种系统的、明确的管理方法。针对软件生命周期中由不断出现的需求变更引起的技术债务,提出一种需求变更技术债务定义。通过对需求变更技术债务的定义、检测、量化和排序,为需求变更的实现顺序以及实现方式提供技术支持。最后通过实验验证了需求变更技术债务的概念和技术的可行性。     

基于CMM2的需求变更管理研究

作为软件工程的一个重要领域,软件需求管理一直受到人们重视。由于软件项目中的需求变更而导致软件项目失败的案例越来越多,所以解决需求变更的问题己经被许多软件公司列入了重要的流程化管理中。在介绍了cMM模型和需求管理的概念后．详细分析了需求变更产生的原因、带来的影响,并提出若干相应的对策。     

Towards a variable size sliding window model for frequent itemset mining over data streams

Sliding window is a widely used model for data stream mining due to its emphasis on recent data and its bounded memory requirement. The main idea behind a transactional sliding window is to keep a fixed size window over a data stream. The window size is kept constant by removing old transactions from the window, when new transactions arrive. Older transactions of window are removed irrespective to whether a significant change has occurred or not. Another challenge of sliding window model is determining window size. The classic approach for determining the window size is to obtain it from the user. In order to determine the precise size of the window, the user must have prior knowledge about the time and scale of changes within the data stream. However, due to the unpredictable changing nature of data streams, this prior knowledge cannot be easily determined. Moreover, by using a fixed window size during a data stream mining, the performance of this model is degraded in terms of reflecting recent changes. Based on these observations, this study relaxes the notion of window size and proposes a new algorithm named VSW (Variable Size sliding Window frequent itemset mining) which is suitable for observing recent changes in the set of frequent itemsets over data streams. The window size is determined dynamically based on amounts of concept change that occurs within the arriving data stream. The window expands as the concept becomes stable and shrinks when a concept change occurs. In this study, it is shown that if stale transactions are removed from the window after a concept change, updated frequent itemsets always belong to the most recent concept. Experimental evaluations on both synthetic and real data show that our algorithm effectively detects the concept change, adjust the window size, and adapts itself to the new concepts along the data stream.     

An approach for sub-ontology evolution in a distributed health care enterprise

In response to the changing nature of health issues, standardized health ontologies such as SNOMED CT and UMLS incline to change more frequently than most other domain ontologies. Yet, semantic interoperability shared among institutions within a distributed health care enterprise relies heavily on the availability of a valid and up-to-date standardized ontology. In this paper, we propose the creation and preservation of sub-ontologies to deal with the frequent changes in health ontologies. Our approach focuses on the nature and characteristics of standard health ontologies, however it can also be applied to other domain ontologies with similar characteristics. Our sub-ontology evolution approach defines ways to create valid sub-ontologies for each specific health application, and to effectively develop a series of propagation mechanism when the main ontology changes. Our approach will (i) isolate the required change propagation to the relevant health applications that utilized the changing concepts only, and (ii) optimize the propagation mechanism to include the minimum number of operations only. Since a sub-ontology should be a valid ontology by itself, the change propagation approach used in this process should contain the rules to assure the validity of the produced sub-ontology while keeping the consistency of the sub-ontology to the evolved base ontology. A change identification process, which considers the nature of the health ontology change logs, is conducted to identify the semantics of the changes. From the evaluation, it is shown that the content of the evolved sub-ontologies produced using our approach is consistent to the evolved base ontology. Moreover, the propagation process can be performed more efficiently because the number of operations required for our change propagation method is lower than the number of operations required for direct re-extraction from the evolved base ontology.     

基于缓存的JCVM性能优化方法研究

传统的JCVM在实例创建技术和事务处理技术存在的一些缺点限制了JCVM的性能,并且在设计上没有充分考虑硬件技术的发展。针对此问题,本文提出了一种基于缓存机制的实例创建技术和一种新的保证事务处理原子性的机制,通过减少不必要的EEPROM写操作来提升JCVM的执行性能。     

A self-adaptable scheduler for synchronizing transactions in dynamically configurable environments

In a database system, the scheduler has the goal of synchronizing operations belonging to several concurrent transactions. The scheduler implements a concurrency control protocol, which may have either conservative or aggressive behavior. Existing database systems have schedulers with static behavior. This paper presents a self-adaptable scheduler, called Intelligent Transaction Scheduler (ITS), which has the ability of dynamically changing its behavior to adapt itself to the characteristics of the computing environment, without any human interference by using an expert system based on fuzzy logic. ITS can implement different correctness criteria, such as classical (syntactic) serializability and semantic serializability.     

过程实例跃迁正确性判定准则研究

过程模型的动态更改会引起运行中的过程实例向更改后的过程模型跃迁,必须保证过程实例跃迁后运行的一致性。由于多分支结构的影响,不同过程实例的跃迁条件不易确定。研究了过程模型更改机制,通过删除、插入、修改三类元更改操作构造更改域。将过程执行历史能否重放作为过程实例跃迁正确性的判定准则,提出一种高效的过程实例精确跃迁条件评判方法,可以确定拥有不同路由结构、不同运行状态的过程实例的跃迁策略。该方法能适应多分支的过程模型,灵活性高,便于实现过程模型动态更改和实例跃迁的自动化。     

A framework for ensuring consistency of Web Services Transactions

For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web service operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transactions, which can spoil data integrity and cause incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transactions. The mechanism effectively detects inconsistent states of transactions with a notion of an end-state dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy integration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.     

Change Management Support to Preserve Business–Information Technology Alignment

Organizations introduce changes to adapt themselves to the extremely changing context. These changes often impact business and information technology (IT) domains. In most of the cases, the scope of the organizational elements in these domains requiring adaptation is not well defined, leaving out elements, what can lead to misalignment. Thus, it is important to know the impact scope in order to perform a full adaptation. When reviewing the literature in the business–IT alignment field, we found that there are no works dealing with this aspect. To fulfill this lack, we carry out a systematic review of change management works and find out a set of clues. We apply them to the business–IT alignment field and as a result propose a change management metamodel, a set of rules and an algorithm to forecast impact scope and adaptations. To operationalize our contributions, we propose a software and demonstrate its applicability through a case study.     

时空变化知识表达模型

为了消除时空变化表达过程中语义的不一致性,将时空变化前后的实体集、变化类型、规则作为变化表达的3个基本元素,利用数据+知识包的形式建立了基于3个基本元素的时空变化表达的三元模型CAR,即变化类型C、变化属性集A和变化判定规则集R,其中规则集中的规则利用IF－THEN方式描述,利用属性集A和规则集的运算判定C,从而解决了目前时空变化表达方法存在的无法表达变化原因的缺陷,而且规则表达便于计算机程序实现。     

Detecting the change of customer behavior based on decision tree analysis

Abstract: Understanding and adapting to changes in customer behavior is an important aspect for survival in a continuously changing environment. This paper develops a methodology based on decision tree analysis to detect the change in classified customer segments automatically between two data sets collected over time. We first define three types of changes as the emerging pattern, the unexpected change and the added/perished rule. Then, similarity and difference measures are developed for rule matching to detect all types of change. Finally, the degree of change is developed to evaluate the amount of change. Our suggested methodology based on decision tree analysis in the change detection problem can be used in more structured situations in which the manager has a specific research question and it also detects the change of classification criteria in a dynamically changing environment. A Korean Internet shopping mall case is evaluated to represent the performance of our suggested methodology, and practical business implications for this methodology are also provided. We believe that the change detection problem and the suggested methodology will become increasingly important as more data mining applications are implemented.