Authorization administration in a distributed multi-application environment

To meet the authorization administration requirements in a distributed computer network environment, this paper extends the role-based access control model with multiple application dimensions and establishes a new access control model ED-RBAC(Extended Role Based Access Control Model) for the distributed environment. We propose an extendable hierarchical authorization assignment framework and design effective role-registering, role-applying and role-assigning protocol with symmetric and asymmetric cryptographic systems. The model can be used to simplify authorization administration in a distributed environment with multiple applications.     

Architecture of HLA based distributed virtual geographic environment

IntroductionDVGE was first proposed by Lin Hui and GongJianhua in 1999. DVGE“is not only an advanceddevelopment of geographic information science, butalso a distributed three dimensions virtual environ-ment. It is based on avatar and has many charac-ters…     

Architecture of HLA based distributed virtual geographic environment

Integrating the theory of distributed virtual geographic enviroments (DVGE) and high level architecture(HLA), the architecture of DVGE based on HLA is designed. The data flow and the object models of the architecture are also discussed. The architecture basically meets the need of DVGE in real-time communication, distribution, collaboration, reusing and interoperation, expansion, and standard.     

分布式虚拟地理环境中时间同步问题研究

分布式虚拟地理环境中的时间同步问题是达成系统时空一致,确保仿真正确,是用户对虚拟地理环境形成正确认识的前提条件。文中针对分布式虚拟地理环境中3个时间概念,重点对机器时间和仿真时间同步问题进行研究,基于网络延时、各仿真节点时间偏移和PC机及操作系统本身时间分辨率不高的因素对时间不同步造成的影响,提出时间同步自适应模型和算法。     

属性委托授权逻辑系统中的主观信任控制

扩展了现有的属性委托授权机制的二值信任为主观区间信任,提出了可信角色和信任约束概念的定义,建立了依据角色信任评估的角色委托控制策略,建立了依据实体信任评估的授权控制规则,给出了委托策略中实体信任度递减的计算方法,将这些策略和规则用逻辑的语法形式表示,并进一步对逻辑程序赋予计算推导的语义,在属性委托授权机制的逻辑语义基础上实现了委托和授权的主观信任控制。     

DCAD: a dual clustering algorithm for distributed spatial databases

Spatial objects have two types of attributes: geometrical attributes and non-geometrical attributes, which belong to two different attribute domains (geometrical and non-geometrical domains). Although geometrically scattered in a geometrical domain, spatial objects may be similar to each other in a non-geometrical domain. Most existing clustering algorithms group spatial datasets into different compact regions in a geometrical domain without considering the aspect of a non-geometrical domain. However, many application scenarios require clustering results in which a cluster has not only high proximity in a geometrical domain, but also high similarity in a non-geometrical domain. This means constraints are imposed on the clustering goal from both geometrical and non-geometrical domains simultaneously. Such a clustering problem is called dual clustering. As distributed clustering applications become more and more popular, it is necessary to tackle the dual clustering problem in distributed databases. The DCAD algorithm is proposed to solve this problem. DCAD consists of two levels of clustering: local clustering and global clustering. First, clustering is conducted at each local site with a local clustering algorithm, and the features of local clusters are extracted. Second, local features from each site are sent to a central site where global clustering is obtained based on those features. Experiments on both artificial and real spatial datasets show that DCAD is effective and efficient.     

DCAD： a Dual Clustering Algorithm for Distributed Spatial Databases

Spatial objects have two types of attributes: geometrical attributes and non-geometrical attributes, which belong to two different attribute domains (geometrical and non-geometrical domains). Although geometrically scattered in a geometrical domain, spatial objects may be similar to each other in a non-geometrical domain. Most existing clustering algorithms group spatial datasets into different compact regions in a geometrical domain without considering the aspect of a non-geometrical domain. However, many application scenarios require clustering results in which a cluster has not only high proximity in a geometrical domain, but also high similarity in a non-geometrical domain. This means constraints are imposed on the clustering goal from both geometrical and non-geometrical domains simultaneously. Such a clustering problem is called dual clustering. As distributed clustering applications become more and more popular, it is necessary to tackle the dual clustering problem in distributed databases. The DCAD algorithm is proposed to solve this problem. DCAD consists of two levels of clus- tering: local clustering and global clustering. First, clustering is conducted at each local site with a local clustering algorithm, and the features of local clusters are extracted. Second, local features from each site are sent to a central site where global clustering is obtained based on those features. Experiments on both artificial and real spatial datasets show that DCAD is effective and efficient.     

分布式环境监测分析WebGIS的设计与实现

实现人类社会的可持续发展必须以客观环境的大力保护为基础,而科学及时的环境监测是人类准确掌握生存环境的变化以制定合理的应对措施,并最终达到环境保护目的。针对现有环境监测站点难以实现实时或准实时的环境监测信息报送及分析的现状,本文基于分布式的地理信息系统平台,设计实现了某省的分布式环境监测网络地理信息系统,服务于环境状况监测信息的分析与发布。     

Data fusion in distributed multi-sensor system

This paper presents a data fusion method in distributed multi-sensor system including GPS and INS sensors' data processing. First, a residual \Gc2-strategy with the corresponding algorithm is designed. Then a coefficient matrices calculation method of the information sharing principle is derived. Finally, the federated Kalman filter is used to combine these independent, parallel, real-time data. A pseudolite (PL) simulation example is given.     

Data Fusion in Distributed Multi-sensor System

This paper presents a data fusion method in distributed multi-sensor system including GPS and INS sensors“ data processing. First, a residual X^2-test strategy with the corresponding algorithm is designed.Then a coefficient matrices calculation method of the information sharing principle is derived. Finally, the federated Kalman filter is used to combine these independent, parallel, real-time data. A pseudolite (PL) simulation example is given.     

分布式计算环境下网络GIS实现技术探讨

介绍了分布式计算环境和网络地理信息系统的概念,探讨了分布式计算环境下网络地理信息系统的几种实现方法,最后对未来的分布式网络地理信息系统发展进行了展望。     

困难环境下的GPS定位实现

本文给出了在困难环境下进行GPS定位的方法,使得在仅能观测3颗甚或2颗卫星时,仍然能够实现三维导航定位,同时对由于卫星几何结构不好导致的法方程病态性问题进行了探讨.仿真结果表明了本文方法的可行性和有效性.     

Building a European geothermal information network using a distributed e-Infrastructure

Geothermal data are published using different IT services, formats and content representations, and can refer to both regional and global scale information. Geothermal stakeholders search for information with different aims. E-Infrastructures are collaborative platforms that address this diversity of aims and data representations. In this paper, we present a prototype for a European Geothermal Information Platform that uses INSPIRE recommendations and an e-Infrastructure (D4Science) to collect, aggregate and share data sets from different European data contributors, thus enabling stakeholders to retrieve and process a large amount of data. Our system merges segmented and national realities into one common framework. We demonstrate our approach by describing a platform that collects data from Italian, French, Hungarian, Swiss and Icelandic geothermal data providers.     

一种面向DVGE的移动Agent计算模型

讨论了移动Agent技术的特点及其在分布式虚拟地理环境(distributed virtual geographic environment,DVGE)中的应用优势,设计了混合式Agent控制结构,提出了一种移动Agent计算模型,并就移动A-gent开发平台选择、动态路由控制策略、用户和共享资源管理等与原型系统实现相关的一些关键问题进行了讨论。     

城市GIS社会化应用中的分布式数据组织方法研究

社会化应用是城市GIS重要的发展方向,城市GIS社会化应用中对于分布于不同城市管理部门的空间数据和属性数据的管理一直是一个比较棘手的问题。本文分析了城市GIS社会化应用的内容和总体结构,提出了基于Oracle分布式数据库的数据组织方案,并对该方法进行了验证。     

Construction of a virtual lunar environment platform

Abstract

Many of the world's powerful and wealthy nations, including China, have devoted both large amounts of funding and considerable promotion to lunar research and exploration. The launch of Chinese Chang'e-1 satellite and the construction of the scientific observation data platform created a favourable opportunity for research into the lunar geometrical, physical and chemical environment. Based on this background, a Wide Area Network (WAN) based virtual lunar environment was constructed for observation data sharing and further exploration. The systematic architecture and framework were introduced and then strategies of mass data (e.g. lunar digital elevation model, lunar digital orthophoto map and typical thematic lunar data) organisation, integration, management and scheduling were then set up to achieve the 3D visualisation of typical lunar geomorphic features. Furthermore, the integration method of 3D lunar data and the process model of impact craters were studied; thus, the whole lunar and celestial collision process could be dynamically simulated. The results indicate that the WAN-based virtual lunar platform can be used effectively for public information sharing, scientific exploration and further to promote the development of deep space exploration in China.     

混合访问控制模型在测绘应用系统中的应用

本文在分析测绘系统开发与应用中测绘数据的复杂性,以及大部分测绘系统都包含业务流程等特点的基础上,除了RBAC模型的角色授权外,加入了任务对操作进行授权,对RBAC模型进行了有效的扩展,使其更具通用性。该方法有效解决了传统的RBAC模型在测绘系统应用中存在的弊端,对其他应用系统建设同样具有理论指导。     

虚拟地理环境中地图注记的配置研究

在虚拟地理环境的表示中注记配置是一个重要方面,注记配置的好坏直接影响着虚拟地理环境的表达.为此,本文从虚拟地理环境的特点出发,分析了三维环境中注记配置研究存在的不足,主要探讨了注记配置应解决的关键问题、配置规则以及配置参数的质量评价原则.     

An incremental LOD method based on grid and its application in distributed terrain visualization

Incremental LOD can be transmitted on the network as a stream, then users on the clients can easily catch the skeleton of terrain without downloading all the data from the server. Detailed information in a local part can be added gradually when users zoom it in without redundant data transmission in this procedure. To do this, an incremental LOD method is put forward according to the regular arragnement of grid. This method applies arbitrary sized grid terrains and is not restricted to square ones with a side measuring 2k+1 samples. Maximum height errors are recorded when the LOD is preprocessed and it can be visualized with the geometrical Mipmaps to reduce the screen error.     

分布式空间数据库中矢量数据多级空间索引方法研究

随着网格计算、云计算等技术在地理信息领域的应用,海量空间数据的高效组织与管理成为提供各种数据和功能服务的基础,空间索引是其中的关键问题,文中在分布式空间数据库系统架构基础上,提出一种适应分布式环境下的分层+分块的矢量数据存储组织模型,设计包括矢量数据面片索引、矢量数据层索引、矢量数据块索引以及数据块内索引在内的多级空间索引。实现表明,文中设计的空间索引支持并发创建和高并发条件下的数据高效访问。