THE VIEWER

xpg displays relations as tables inside a scrollable area.  Attribute names are displayed above this area, and automatically scroll in synchronization with the horizontal scrolling of the table.  Both attributes and tuples are selectable; selected attributes are called "key attributes", or simply "keys" (see the KEY ATTRIBUTES section); tuples are selected by dragging the mouse over a set of tuples (dragging is moving the mouse pointer while holding the mouse button pressed).  You can also toggle individual tuples by pressing the Ctrl key and the mouse button over a tuple.  xpg provides Replace and Delete operations which operate on a selected set of tuples; see the CLASS OPERATIONS section for more information on these operations.

Viewing a relation is most times the first thing you must do in order to access the various features of xpg for the specific relation.  In order to perform Class Operations, printing, Math Operations, etc., the viewer must contain a relation first.  Script playing does not require this, because scripts are global to the database and thus do need to be related to any relation.