Data - object containing undo information for storage in a
       command

SYNOPSIS

       #include <Unidraw/Command/data.h>

DESCRIPTION

       Data is an abstract base class for objects that components
       store in commands they (un)interpret.  Components use Data
       subclasses to store  whatever  information  they  need  to
       uninterpret the command.

PROTECTED OPERATIONS

       Data() The  constructor is protected to prevent instantia-
              tion.

SEE ALSO

       Command(3U), Component(3U), Resource(3I)