Datasources Node

The Datasources node in the Workspace Manager manages all opened datasources in the workspace. A datasource can contain a set of datasets of different types. You can create, open, close datasources through the commands provided in the context menu for the Datasources node.

Datasource

A datasource stores spatial data independent of a workspace. As to products, datasources can be stored in local or online files or databases. Based on how and where datasources are stored, there are three types: file datasoruce, database datasource and web datasource.

1. File Datasources, namely, the UDB datasources, are stored in an *.udb or *.udd file. When creating an UDB datasource, an .udb file and a corresponding .udd file are generated. And when creating a UDB datasource, a .udb file and a corresponding .udd file will be generated.

   GIS spatial data include spatial geometry objects and their properties. In a file datasource, an *.udb file mainly stores the geometry information of spatial data. An *.udd file stores the properties information. A datasource file only corresponds to a datasource.

   A UDB datasource is a cross-platform file datasoruce that supports efficient access to massive data. A UDB datasource can store 128TB of data at most.

2. Database Datasources are datasources stored in databases, such as Oracle Plus databases and SQL Server Plus databases. Both the spatial information and attribute information of the database datasource are stored in databases.

   To operate data in a datasource, you must open the datasource first. All operations conducted on the datasource are directly saved to the datasource instead of the workspace because the datasource is stored independent of the workspace and the workspace only provides the reference to the datasource. Presumably, a datasource will not be deleted when the workspace is deleted.

3. Web Datasources are stored on web servers and accessed through URL addresses.

You are permitted to open different types of datasources in a workspace. Often, spatial data for a certain use is organized in the same datasource to facilitate efficiency.

Dataset

Geographic features are representations of things located on or near the surface of the earth. Geographic features can occur naturally (such as rivers and vegetation), can be constructions (such as roads, pipelines, wells, and buildings), and can be subdivisions of land (such as counties, political divisions, and land parcels). We use datasets, collections of geographic features of the same type, to represent a geographic area. For instance, we use point datasets, collections of points, to represent geographic features too small to be depicted as lines or polygons, such as well location, telephone poles, and buildings. We use line datasets, collections of lines, to represent geographic features too narrow to be depicted as areas, such as streets and streams, or slices through a surface, such as contours. And we use region datasets, collections of closed figures, to represent the shape and location of homogeneous features, such as states, counties, parcels, soil types, or land-use zones. Therefore, a datasource consists of a set of datasets of different types. Actually, except for representing a geographic area with point datasets, line datasets, and region datasets, many other dataset types are also employed to represent the information in the geographic area. These datasets include: tabular datasets, network datasets, CAD datasets, text datasets, lineM datasets, image datasets, and grid datasets.

A dataset is a basic unit for spatial data organization, and can be displayed in a map window as a layer. You can edit a dataset in a map window, such as move the geometric objects to a new position, obtain a line dataset through vectorizing an image dataset, etc.