Whereas two other basic types of EDB components – tables and queries – are nearly analogous to basic notions of the theory of databases, EDB layers does not have such analogs in theory. Layers are specialized components of the ObjectLand EDB intended to store spatial features, just as these features are stored in the ObjectLand map's layers. The difference is in the fact that in case of EDB layers all the information about features, their types and properties is stored outside the ObjectLand GDB. When creating an EDB layer, additional tables are created in the data source, and these tables contain all the information on types, coordinates and properties of features.
Not all types of external data sources provide the possibilities to create layers. For instance, when Microsoft Excel sheets or text files are used as data sources, the creation of layers is impossible. On the other hand, Microsoft Access databases provide sufficient functional capabilities to create layers.
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