The OODB path-method generator (PMG) using access weights and precomputed access relevance

A path-method is used as a mechanism in object-oriented databases (OODBs) to retrieve or to update information relevant to one class that is not stored with that class but with some other class. A path-method is a method which traverses from one class through a chain of connections between classes and accesses information at another class. However, it is a difficult task for a casual user or even an application programmer to write path-methods to facilitate queries. This is because it might require comprehensive knowledge of many classes of the conceptual schema that are not directly involved in the query, and therefore may not even be included in a user's (incomplete) view about the contents of the database. We have developed a system, called path-method generator (PMG), which generates path-methods automatically according to a user's database-manipulating requests. The PMG offers the user one of the possible path-methods and the user verifies from his knowledge of the intended purpose of the request whether that path-method is the desired one. If the path method is rejected, then the user can utilize his now increased knowledge about the database to request (with additional parameters given) another offer from the PMG. The PMG is based on access weights attached to the connections between classes and precomputed access relevance between every pair of classes of the OODB. Specific rules for access weight assignment and algorithms for computing access relevance appeared in our previous papers [MGPF92, MGPF93, MGPF96]. In this paper, we present a variety of traversal algorithms based on access weights and precomputed access relevance. Experiments identify some of these algorithms as very successful in generating most desired path-methods. The PMG system utilizes these successful algorithms and is thus an efficient tool for aiding the user with the difficult task of querying and updating a large OODB. Received July 19, 1993 / Accepted May 16, 1997     

基于多色图理论的协同设计多级版本管理模型

针对产品协同设计过程中版本管理模型的问题进行研究.通过对现有的版本管理模型优缺点进行分析,在多色集合理论和多色图理论研究的基础上,结合产品协同设计版本具有多版本、动态性和关联性的特点,提出了基于多色图理论的协同设计多级版本管理模型,并给出其形式化描述与定义,给出了一个实例,利用该模型实现版本的回溯算法,证明了模型的有效性.     

A decidable first-order logic for knowledge representation

Decidable first-order logics with reasonable model-theoretic semantics have several benefits for knowledge representation. These logics have the expressive power of standard first order logic along with an inference algorithm that will always terminate, both important considerations for knowledge representation. Knowledge representation systems that include a faithful implementation of one of these logics can also use its model-theoretic semantics to provide meanings for the data they store. One such logic, a variant of a simple type of first-order relevance logic, is developed and its properties described. This logic, although extremely weak, does capture a non-trivial and well-motivated set of inferences that can be entrusted to a knowledge representation system.This is a revised and much extended version of a paper of the same name that appears in the Proceedings of the Ninth International Joint Conference on Artificial Intelligence, Los Angeles, California, 1985.     

Computing access relevance for path-method generation in OODB and IM-OODB

A path-method (PM) is a mechanism to retrieve or to update information relevant to one class, in an object-oriented database (OODB), that is not stored with that class but with some other class. The PM traverses a chain of classes and connections that ends at the class where the required information is stored. However, it is a difficult task for a user to write PMs. This is because it might require comprehensive knowledge of many classes of the conceptual schema. But a typical user has often incomplete or even inconsistent knowledge of the schema. Currently we are developing a system, called Path-Method Generator (PMG), which generates PMs automatically according to a naive user's requests. One algorithm of PMG uses numerical access relevance between pairs of classes as a guide for the traversal of an OODB schema. In this paper we define the notion of access relevance to measure the significance of the (indirect) connection between any two classes in an OODB and present efficient algorithms to compute access relevance. The manual PM generation in an interoperable multi object-oriented database (IM-OODB) is even more difficult than for one OODB since a user has to be familiar with several OODBs. We use a hierarchical approach for developing efficient online algorithms for the computation of access relevances in an IM-OODB, based on precomputed access relevances for each autonomous OODB. In an IM-OODB the access relevances are used as a guide in generating PMs between the classes of different OODBs.     

基于LDA模型的新闻话题的演化

新闻话题及演化的研究可以帮助人们快速了解和获取新闻内容。提出了一种挖掘新闻话题随时间变化的方法,通过话题抽取和话题关联实现话题的演化。首先应用LDA(Latent Dirichlet Allocation Model)对不同时间段的文集进行话题的自动抽取,话题数目在不同时间段是可变的;计算相邻时间段中任意两个话题的分布距离实现话题的关联。实验结果证明该方法不但可以描述同一个话题随时间的演化过程,还可以描述话题内容随时间的变化,反映了话题(或子话题)之间多对多的演化关系。     

基于门限关联度的多特征量性能可靠性评估

针对具有多个特征参量的产品性能可靠性评估问题,提出一种基于门限关联度的多特征量性能可靠性评估方法.该方法利用灰色系统理论中的多参数关联分析方法计算多性能特征量的待检状态与标准状态的关联度,通过关联度的大小来判断系统的性能状况,进而对系统的性能可靠性进行评估.最后以某电路为例,对其监测数据分析得出给定时间条件下,该电路的性能可靠度为0.75,从而验证了该方法的有效性和实用性.     

基于蝙蝠算法优化相关向量机的轴承故障诊断方法

由于轴承振动信号具有复杂性和非线性,难以有效提取故障特征,影响故障诊断的准确率.为了提高故障诊断准确率,提出一种蝙蝠算法(BA)优化相关向量机(RVM)的轴承故障诊断方法.首先结合变分模态分解和多尺度熵从轴承振动信号中提取出故障特征,作为相关向量机的输入向量;接着采用蝙蝠算法优化相关向量机的核函数参数;然后训练相关向量...     

基于遗传优化加权相关向量机的网络热点预测模型

为了提高网络热点事件的预测精度,提出一种基于遗传优化加权相关向量机的网络热点事件预测模型(GA-WRVM)。首先对每个样本数据的噪声方差加上一个权值系数得到加权相关向量机,然后用组合核函数代替相关向量机的单一核函数,并采用遗传算法对核参数进行优化建立预测模型,最后利用网络热点数据进行仿真实验分析。结果表明,相对于神经网络和支持向量机,GA-WRVM降低了网络热点事件的预测误差,获得了更高的网络热点预测精度,具有更强的泛化能力。     

颜色、纹理、形状及相关反馈在图像检索中的应用

图像数据库的不断庞大使基于内容的图像检索成为研究热点,目前主要集中于底层特征的相似度匹配。文章重点介绍了颜色特征中的分块主色法,纹理特征中的灰度共生矩阵法和形状特征中的小波变换及不变矩法。在利用单一特征检索的基础上,该文提出了一种综合利用上述三种特征共同进行检索的方法。同时,还将相关反馈技术融合到算法中,通过权值矩阵的正负调整及三种特征系数的调整来提高检索准确率。由实验数据表明,文中的方法是很有效的。     

基于语义与句法的Java类库检索方法与系统

提出了一个支持系统化、大规模软件复用的基于语义与句法的可复用模块的检索方法,并介绍了基于此方法支持Jwa类库的实用检索系统。软件开发者既可以使用自然语言直接描述待开发软件的功能语义并用此查询类库中的相关模块,也可以通过对输入输出数据类型的描述对Java类库进行快速地查询,还可以同时使用两者的组合来提高可复用库模块查询的精度。