How the communication object is loaded into memory is an indication of the purpose of the communication object. A DLL containing a communication object can be loaded into memory in two ways:

• Through use of the :docprof. tag's dll attribute (see :docprof. (Document Profile)). A communication object loaded through the :docprof. tag is considered a "global" communication object because it affects the IPF coverpage window and all of its children IPF windows. Essentially, a :docprof.-loaded communication object can alter the overall behavior and appearance of IPF, such as providing author-defined buttons in the control area or special message handling. You can load only one communication object in this manner.

• Through use of the :acviewport. tags (see :acviewport. (Application-Controlled Window)). A communication object loaded in this way will only affect the specific application-controlled window and only when that window is open. Therefore, a communication object loaded through an :acviewport. tag is useful for tasks such as displaying video clips or bit maps associated with a given help panel. However, if you want a communication object to affect the overall appearance or behavior of the IPF interface for a given help session, you will want to use a "global" communication object (one that is loaded through the :docprof. tag). Unlike a global communication object, you can load multiple :acviewport. communication objects or refer to the same communication object from multiple :acviewport. tags.

An acviewport communication object is called each time a window is opened. A global communication object is called only once.