Creation and saving different themes based on one and the same graphic features set is a very useful tool in ObjectLand which enables the user to easily get the necessary variant of features' display when required. One of the methods of creating new themes was described above. The essence of this method was in opening the theme browser window for one of GDB components, performing all the necessary changes of displaying variant (changing displayed fragment, selecting the necessary set of layers and feature types, setting the desired displaying styles, etc.) and then saving the theme obtained in such a way by assigning an appropriate name for it.
Such a way of creating a theme is good due to its clearness: the system saves what the user sees at the moment of saving. However, this method has one serious drawback. Every time the displaying variant is changed, the system redraws the displaying pane, and for a big and complex map this operation can take considerable time.
Another approach is to create a new theme without using the map browser window. In this case a convenient tool which can be used is the menu command Edit in the navigation window when a theme name is selected. First of all, the user creates a new theme. Then he has a possibility to specify the required displayed fragment in coordinate form, select the necessary layers and feature types for the theme, select displaying styles and specify other characteristics. As a result, the user will build the cataloged theme he needs. After that the browser window will show the final result without intermediate redrawings.
For creating a new theme it is possible to select the component type Themes in hierarchy pane of any navigation window (it is also possible to select any existing theme) and to execute the menu command Edit+Add. The dialog box “Adding theme” shown at figure 14-2 will be opened.
Figure 14-2. Dialog box “Adding theme”
After pushing OK the new theme appears in the list of themes in the navigation window. However the just created theme is empty, i.e. it does not contain any layers to display. To add layers one should select the theme's name in the hierarchy pane, then activate the layer list pane (click in this pane) and execute the menu command Edit+Add. Dialog box “Adding layers” is shown at figure 14-3.
Figure 14-3. Dialog box “Adding Layers”
The box contains two radio buttons Available layers and Create work layer. The list of layers available for adding into the theme comprises all layers of all GDB maps and of all opened external databases with the exception of those layers which are already included in the given theme. The user can mark one or several layers for their including into the theme, and these layers can belong to different maps and EDB's.
Creation of work layers will be considered in the subsection “Work layers of a theme”.
Now the theme contains the prescribed set of layers but the layers themselves are yet empty, because adding a map layer in a theme does not imply automatic adding feature types of that layer.
To add feature types one should select a map layer in the hierarchy pane, then activate the list pane (left click in this pane) and execute the menu command Edit+Add. Dialog box “Adding feature types” is shown at figure 14-4.
Figure 14-4. Dialog box “Adding feature types”
The list in the dialog box' pane comprises those feature types of the corresponding map layer which are not included in the given layer of the theme. The user can select one or several types for their including into the layer of the theme.
After the theme is created the user can open it for browsing (menu command Edit+Open or the button 
), change properties of the theme and of its components (menu command Edit+Properties or the button 
) and perform some other operations.
Another possibility to create a theme in the navigation window is duplication of one of existing themes. For that, one should select an appropriate theme in a window's pane and execute the menu command Edit+Duplicate. In the dialog box “Duplication of theme” the name of a new theme should be entered. The created theme will be identical to the source one in its component set and their properties. Further the user can make necessary changes in the theme.
To introduce changes into the cataloged theme, the user can take the following actions:
To view and change the theme properties (for example, coordinates of displayed fragment) it is necessary to perform the menu command Edit+Properties.
To change the set of layers and feature types included into the theme, it is required to select the corresponding theme component (layer or type) and then perform the commands Edit+Add, Edit+Remove. It is also possible to change the order of displaying layers by performing the command Edit+Order.
To change the properties of separate layers and feature types (for example, select a specific layer or feature type displaying style) it is necessary to select the corresponding component and perform the command Edit+Properties.
To rename the selected theme it is required to perform the command Edit+Rename or just click the name of the selected theme again and then enter its new name.
To remove the selected cataloged theme the command Edit+Remove should be executed.
If the very first theme is created for the present GDB one should select the word “Themes” in the left pane of the navigation window and call the menu Edit which in this case contains only one command Add.
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