SuperMap manages the symbols in the symbol library by logical grouping, and the Marker Symbol Library, Line Symbol Library, and Fill Symbol Library all use the same logical management method.

In order to better understand the management of symbolic logical grouping, we can understand the management of symbolic logical grouping by analogy with the way Windows Explorer uses folders to manage disk files. In the following description, the symbol logical grouping is referred to as the symbol grouping.

Windows Explorer organizes files through folders and classifies and stores files. In fact, files are stored on the disk. There is no concept of folder on the disk. Folder is only a logical management organization of files. In order to facilitate users to manage, find and use files. For example:

• The path "C: \" represents the root directory of the disk. The root directory contains a series of files and folders, and each folder contains a series of files and folders. By analogy, a folder can contain files or nest other folders.
• When we locate a file stored in a certain location of the C disk, we locate it through the path of the folder. The absolute path of the file is the path formed by the folder from the root directory of the C disk to the Target Storage location of the file. For example, the "C: \ SuperMap \ Data \ City \" Changchun. UDB "indicates the absolute storage path of the Changchun. UDB file.

The logical grouping management of the symbol library involves the following concepts: root group, symbol grouping, and symbol:

• Root group: The root group of the symbol library is the root directory of the logical management organization of the symbol library, which is equivalent to the root directory of the disk in the logical management organization of the Windows Explorer, for example, equivalent to the "C: \" root directory;
• Symbol Grouping: Symbol Grouping is a subdirectory under the root group of the symbol library. Symbol Grouping is equivalent to the folder in the logical management organization of Windows Explorer. The folder has the Folder Name, and correspondingly, the symbol grouping also has the name of the symbol grouping;
• Symbols: Symbols are equivalent to files.
• Same as the logical management organization of Windows Explorer, the symbol root group can contain several symbols and several symbol groups; each symbol group can contain several symbols and symbol groups, that is, the symbol groups can be nested, and so on, so that the symbols stored in the symbol library can be classified, stored and managed.
• The symbol storage position is located in the symbol library, that is, the symbol group where the symbol is located is also located through a path, and the path is an absolute path which is the path formed by all symbol groups passing through from the symbol root group to the target symbol group where the symbol is located, For example, "Root Group \ Group A \ Group C" indicates that the symbol content under the symbol group named "Symbol Group C" can be browsed.
• In Windows Explorer, you can place a new file in New Folder under any path, and then store the new file in the new folder; or move a file under another path to another path. Corresponding to the symbol library, the effect described above can also be achieved. A new symbol group can be created in any symbol group, and Add Symbol in the symbol group; or Move Symbol to another symbol group, that is, change the storage path of the symbol.
• Similar to folder management, symbol groups with the same name cannot exist in the same symbol path;
• The symbols in the symbol library are numbered each symbol by the symbol number Unique identifier, and any symbol in a symbol library has a unique number.

The following figure takes the Marker Symbol Library as an example to vividly show the logical storage structure of the symbol library and the analogy between the logical organization form of the symbol library and the Windows Explorer.

Diagram of the logical organization of the Marker Symbol Library.