CAD/CAM网站中动态页面的设计

介绍了CAD CAM网站中动态页面的设计。为了实现用户与网站的交互功能 ,在词汇查询与问题讨论部分采用ASP技术 ,使本站能够根据用户的需求在数据库中调取相关数据 ,动态生成页面。     

浅论Solidworks中尺寸公差标注的二次开发

主要介绍了以VB为开发工具,用ACCESS建库,利用Solidworks OLE应用程序开发接 口API函数实现Solidworks中尺寸公差查询模块系统的研究和开发。该模块解决了Solidworks中不 能动态查询尺寸公差的问题。     

分布式数据库半连接查询优化算法的研究

在分布式数据查询处理中,连接操作是最常用的、费时的而且代价较高的一种操作,也是影响查询效率的关键因素。在处理连接操作的优化时,通常采用半连接的方法来缩减操作数,减少网络传输代价,降低通信费用。本文在研究前人的传统算法基础上,针对半连接操作提出了一种新的改进算法,在处理分布式数据库中海量信息查询和复杂查询领域里具有实用的价值。     

基于Hive的空气质量大数据查询优化方法

为了提高对环境空气质量监测系统中省级环境监测中心站里已汇集的海量监测数据的统计和分析效率,提出了一种基于Spark 集群在Hive上进行多维数据分区的查询优化方法。以湖北省环境监测中心站中的空气质量监测数据为研究对象,将数据转移到Spark集群利用Spark SQL连接Hive并进行分区存储。设计了12种查询,查询4个数据集,通过与采用传统查询方法的实验对比得出结论。实验结果表明:基于Hive的分区优化方法对空气质量大数据的查询时间有47%到96%的优化,而随着查询的复杂程度和数据量的增加,该方法的优化效果越明显。     

长庆油田质量安全环保巡察实践

随着电力业务的不断扩展,勘测积累了大量的工程相关资料,目前大多存储分散,查询调用较为烦琐,再次利用率也非常低。针对电力勘测数据的特点,通过对开源JavaSctipt库和Cesium三维可视化关键技术的研究,设计了一套包含二、三维数据录入、三维可视化展示,数据查询、分析利用以及数据库管理的电力工程数据管理平台,为提高勘测数据管理效率,充分挖掘利用已有数据资源提供信息技术支持。     

Inference control of open relational queries under closed-world semantics based on theorem proving

Relational database systems may serve to evaluate an open query under closed-world semantics. The evaluation returns an explicit output relation complemented with an often implicit statement about the completeness of that relation. The output relation is formed from all those tuples that both fit the format and satisfy the properties expressed in the query. Using first-order logic for specifying formal semantics, the output relation can be seen as a set of (ground) sentences obtained from the query formula by suitable substitutions of free variables by constants. A statement about the completeness of a relation can also explicitly be formalized as a sentence of first-order logic. Inference control for enforcing a confidentiality policy has to inspect and to possibly distort not only the sentences representing the tuples of the output relation but also the completeness sentences. Previously designed and formally verified control procedures employ theorem-proving for such inspections while iteratively considering candidates for those sentences and determining termination conditions, respectively. In this article, we outline an implementation of these control procedures and treat improvements of their runtime efficiency, in particular to overcome shortcomings of the underlying theorem prover, which is repeatedly called with an input comprising a completeness sentence of increasing size. The improvements are obtained by an equivalent rewriting of completeness sentences, exploiting the active domain or introducing new constants for combinations of the original constants, respectively, as well as by optimizing the number of such calls. Besides theoretical complexity considerations, we also present practical evaluations for some examples. These examples include queries that—without control—would return the whole underlying database relations and—with control—can be used for confidentiality-preserving data publishing.     

面向未来互联网的感知服务发现方法研究

要解决现有互联网管控能力弱的问题,未来互联网就必须具备强大的网络感知。面向服务的未来互联网将感知信息作为一种创新的服务和应用来增强网络的感知能力,如何快速发现和获取所需的感知服务信息成了必须要解决的重要问题之一。提出一种基于DHT的分布式服务发现方法。该方法利用分层的服务描述使得在保证查询的准确性和效率的同时,更能够支持复杂查询,并通过仿真工具Over Sim验证了该方法的性能。     

Visual query interfaces for semantic datasets: An evaluation study

The rapid growth of the Linked Open Data cloud, as well as the increasing ability to lift relational enterprise datasets to a semantic, ontology-based level means that vast amounts of information are now available in a representation that closely matches the conceptualizations of the potential users of this information. This makes it interesting to create ontology based, user-oriented tools for searching and exploring this data. Although initial efforts were intended for tech users with knowledge of SPARQL/RDF, there are ongoing proposals designed for lay users. One of the most promising approaches is to use visual query interfaces, but more user studies are needed to assess their effectiveness. In this paper, we compare the effect on usability of two important paradigms for ontology-based query interfaces: form-based and graph-based interfaces. In order to reduce the number of variables affecting the comparison, we performed a user study with two state-of-the-art query tools developed by ourselves, sharing a large part of the code base: the graph-based tool OptiqueVQS*, and the form-based tool PepeSearch. We evaluated these tools in a formal comparison study with 15 participants searching a Linked Open Data version of the Norwegian Company Registry. Participants had to respond to 6 non-trivial search tasks using alternately OptiqueVQS* and PepeSearch. Even without previous training, retrieval performance and user confidence were very high, thus suggesting that both interface designs are effective for searching RDF datasets. Expert searchers had a clear preference for the graph-based interface, and mainstream searchers obtained better performance and confidence with the form-based interface. While a number of participants spontaneously praised the capability of the graph interface for composing complex queries, our results evidence that graph interfaces are difficult to grasp. In contrast, form interfaces are more learnable and relieve problems with disorientation for mainstream users. We have also observed positive results introducing faceted search and dynamic term suggestion in semantic search interfaces.     

Approximation and relaxation of semantic web path queries

Given the heterogeneity of complex graph data on the web, such as RDF linked data, it is likely that a user wishing to query such data will lack full knowledge of the structure of the data and of its irregularities. Hence, providing flexible querying capabilities that assist users in formulating their information seeking requirements is highly desirable. In this paper we undertake a detailed theoretical investigation of query approximation, query relaxation, and their combination, for this purpose. The query language we adopt comprises conjunctions of regular path queries, thus encompassing recent extensions to SPARQL to allow for querying paths in graphs using regular expressions (SPARQL 1.1). To this language we add standard notions of query approximation based on edit distance, as well as query relaxation based on RDFS inference rules. We show how both of these notions can be integrated into a single theoretical framework and we provide incremental evaluation algorithms that run in polynomial time in the size of the query and the data, returning answers in ranked order of their ‘distance’ from the original query. We also combine for the first time these two disparate notions into a single ‘flex’ operation that simultaneously applies both approximation and relaxation to a query conjunct, providing even greater flexibility for users, but still retaining polynomial time evaluation complexity and the ability to return query answers in ranked order.