Group Expressions

 A ``group expression'' is a string which identifies a group of objects (eg numerical values, NDFs, etc). A group expression can specify a group of such objects in several ways:

• As a comma separated list ( e.g. ``12.1, 23.2, 1.3'' or ``HH1_B1S1,HH2_B1S2'' ).
• By reading them from a text file (see ``Indirection'').
• By modifying an existing group of objects using editing specified by the user (see ``Modification'').

If the supplied group expression is terminated with a minus sign, the user is re-prompted for another group expression. The objects specified by this second group expression are added to those specified by the first. This re-prompting continues until a group expression is supplied which does not end with a minus sign.

Certain classes of objects have additional features, for instance if the objects are NDF names, then wild-card characters are allowed in the supplied values (see section ).