As it was already described in previous sections, GIS ObjectLand permits storing not only spatial data contained in GDB components – maps, but also attributive data in the form of GDB components – tables, as well as building different representations of this information which are referred to as queries. ObjectLand uses its own format for storing table data.
Today there are a lot of applications available which store and process attributive data specified in the form of tables. First of all, these are various database management systems (DBMS). They are subdivided into “desktop” applications, that is, the ones used to store data on the local computer (Microsoft Access, FoxPro, dBase, Paradox, etc.) and powerful database servers (Oracle, Microsoft SQL Server, InterBase and others). Besides, table data can be stored and processed by spreadsheet programs (Microsoft Excel, etc.) and other applications.
A text file is the simplest form of storing table data. Every line of such a file is a record of the table; one can divide the record into separate fields on the basis of the known width of fields or using the specified separator character.
It is quite possible that the table data necessary to describe objects of ObjectLand maps is already present in the form of data of one application described above. In this case ObjectLand user can choose one of the two ways of actions.
The first way is to import data, that is, transform it into a format of internal tables of ObjectLand. After this process has been completed, imported data is processed by ObjectLand tools and no connection with the data source application is provided for. Possibilities of importing (and exporting) table and spatial data will be presented in section “Import and export of data”.
For table data it is possible to use another method of processing such data in ObjectLand which differs from the previous one completely. The data is retained in the original format, stored separately from GDB, however an ObjectLand user gets a possibility to work with this data like with usual internal tables and queries of GDB (although some limitations may be imposed). This approach is rather convenient, due to the possibility to add and correct data in the application where it was created. Thus, the data is used in ObjectLand, but procedures of updating the data are carried out using another program, and very likely by other people and on a different computer.
In the second variant, table data are considered to be external databases (EDB) with regard to ObjectLand GDB. Only service data about EDB location and the way to connect to it are stored in the GDB structure.
Operating systems of Microsoft Windows family provide developers with means of connection with external data sources known as ODBC (Open Database Connectivity). ODBC provides a set of functions which can be used to access table data of different applications. Forming requests to EDB and manipulation with data in the frame of ODBC technology are performed on the basis of the widely used standard of data managing language called SQL.
 |  |
