Groups can be stored in, and retrieved from a DataBase object. One presents here the methods defined in generic class DataBase, or in its derived classes, and that are devoted to the manipulation of Group objects. In the DataBase, the Group objects are stored in a mapping associating their names to the Group. This association allows to retrieve the Group when needed.
One makes the distinction between the simple manipulation of Groups described in section I.1.2.1 and the more complicated operation where new Groups are created by association operations (section I.1.2.2). The methods related to these associative operations are often defined in the specialized versions of the Database class.