通过对Access World News数据库和Press Display数据库的对比,探讨了全球两大媒体数据库各自的优势、特点和问题,通过案例,分析了图书馆咨询人员面对不同课题需求时数据库的工作策略。提出应该充分发挥各个数据库的功能优势,同时对数据...通过对Access World News数据库和Press Display数据库的对比,探讨了全球两大媒体数据库各自的优势、特点和问题,通过案例,分析了图书馆咨询人员面对不同课题需求时数据库的工作策略。提出应该充分发挥各个数据库的功能优势,同时对数据库自身的各种问题进行人工干预和后期处理,从而对研究课题进行最大程度的资料挖掘和分析。展开更多
World Data Center(WDC)for Seismology,Beijing has developed for 20 years in China until this year.The sustained and stable data sharing service system has already taken shape.This article gives an overview of the const...World Data Center(WDC)for Seismology,Beijing has developed for 20 years in China until this year.The sustained and stable data sharing service system has already taken shape.This article gives an overview of the construction and development of WDC for Seismology,Beijing.It outlines the history,facilities and technical specifications of the center.It also illustrates the data service,the website,and gives a brief description of the perspective.展开更多
It is well-known that there are circumstances where applying Reiter's closed world assump- tion (CWA) will lead to logical inconsistencies . In this paper, a new characterization of the CWA consistency is pesented...It is well-known that there are circumstances where applying Reiter's closed world assump- tion (CWA) will lead to logical inconsistencies . In this paper, a new characterization of the CWA consistency is pesented and an algorithm is proposed for determining whether a datalase with- out function symbols is consistent with the CWA. The algorithm is shown to be efficient.展开更多
网络分布计算环境下应用系统的需求多样化和复杂性的增长,要求位于中间件层次的Web应用服务器(web application server,简称WAS)从原来的尽力而为服务模型转变为服务质量(quality of service,简称QoS)保障模型,为具有不同需求的应用分...网络分布计算环境下应用系统的需求多样化和复杂性的增长,要求位于中间件层次的Web应用服务器(web application server,简称WAS)从原来的尽力而为服务模型转变为服务质量(quality of service,简称QoS)保障模型,为具有不同需求的应用分别提供适宜的服务质量保障.目前的WAS系统在此方面仍然比较薄弱.OnceAS/Q是一个面向QoS的WAS系统,它以QoS规约为基础,为不同应用提供不同的QoS保障能力.OnceAS/Q实现了一个应用QoS保障框架,提供了一组QoS服务组件支持具有QoS需求的应用开发和运行.介绍了OnceAS/Q的体系结构和主要组件,详细阐述了两个关键问题,一是QoS规约的定义及其映射,另一个是面向QoS的服务组件和资源的动态重配.OnceAS/Q原型在Ecperf测试基准下,对其QoS保障能力进行了实验.实验数据表明,在较大规模的应用环境下,OnceAS/Q能够提供更好的服务质量,并且开销是可接受的.展开更多
文摘通过对Access World News数据库和Press Display数据库的对比,探讨了全球两大媒体数据库各自的优势、特点和问题,通过案例,分析了图书馆咨询人员面对不同课题需求时数据库的工作策略。提出应该充分发挥各个数据库的功能优势,同时对数据库自身的各种问题进行人工干预和后期处理,从而对研究课题进行最大程度的资料挖掘和分析。
文摘World Data Center(WDC)for Seismology,Beijing has developed for 20 years in China until this year.The sustained and stable data sharing service system has already taken shape.This article gives an overview of the construction and development of WDC for Seismology,Beijing.It outlines the history,facilities and technical specifications of the center.It also illustrates the data service,the website,and gives a brief description of the perspective.
文摘It is well-known that there are circumstances where applying Reiter's closed world assump- tion (CWA) will lead to logical inconsistencies . In this paper, a new characterization of the CWA consistency is pesented and an algorithm is proposed for determining whether a datalase with- out function symbols is consistent with the CWA. The algorithm is shown to be efficient.
文摘网络分布计算环境下应用系统的需求多样化和复杂性的增长,要求位于中间件层次的Web应用服务器(web application server,简称WAS)从原来的尽力而为服务模型转变为服务质量(quality of service,简称QoS)保障模型,为具有不同需求的应用分别提供适宜的服务质量保障.目前的WAS系统在此方面仍然比较薄弱.OnceAS/Q是一个面向QoS的WAS系统,它以QoS规约为基础,为不同应用提供不同的QoS保障能力.OnceAS/Q实现了一个应用QoS保障框架,提供了一组QoS服务组件支持具有QoS需求的应用开发和运行.介绍了OnceAS/Q的体系结构和主要组件,详细阐述了两个关键问题,一是QoS规约的定义及其映射,另一个是面向QoS的服务组件和资源的动态重配.OnceAS/Q原型在Ecperf测试基准下,对其QoS保障能力进行了实验.实验数据表明,在较大规模的应用环境下,OnceAS/Q能够提供更好的服务质量,并且开销是可接受的.