Service-Based Global Spatial Data Directory in Spatial Information Grid

Spatial Information Grid (SIG) is a spatial information infrastructure that has the capability of providing services on-demand. It provides a new distributed computing pattern for sharing and operating the massive distributed spatial information resources. The global spatial data directory is an information tree organization used to quickly locate spatial data resources and spatial database nodes in SIG and it is a key technology about quickly discovering, querying and locating spatial information resources. In this research, groups of spatial information services and spatial operation services are developed to support spatial data discovery and spatial applications. Spatial database distributed on scattered nodes. They are connected by the network and form a visual super global spatial database. Spatial database on proximity or logically associated nodes combined as a domain spatial database and a domain spatial data directory was built by the local spatial directory service. Directories in different domains build the global spatial data directory by the directory copy and synchronous mechanism. A resource monitoring and discovery service (MDS) was developed to discover new spatial resources and monitor resources' status. Spatial data resources such as layers and digital raster graphics (DRG) were registered to the directory as spatial metadata, and node information and resource security level are also contained in spatial metadata structure. A security spatial resources access control mechanism was implemented based on grid security infrastructure (GSI) and role based access control (RBAC). Global spatial indexes were built by layer type, role permission or minimum bounding rectangle (MBR) based on the global spatial data directory. Spatial data query and quickly locate were well supported by these indexes. Spatial database nodes' dynamic join and exit are also supported, and "Center-Based" global directory's single-point dependence problem was resolved. The Globus Toolkit 4.0 was used as the grid infrastructure in this research.