Over the years a collection of IDE components have been developed, 
each with its own interface. In addition, some of these components 
require each other, and loading IDE components must be on demand to 
avoid the IDE being part of a saved state (see qsave_program/2). 
For this reason, access to the IDE is concentrated on a single interface 
called prolog_ide/1:
- prolog_ide(+Action)
- This predicate ensures the IDE-enabling XPCE component is loaded, 
creates the XPCE class prolog_ide and sends Action to 
its one and only instance @prolog_ide. Action is 
one of the following:
- open_navigator(+Directory)
- Open the Prolog Navigator (see section 
3.6) in the given
Directory.
- open_debug_status
- Open a window to edit spy and trace points.
- open_query_window
- Open a little window to run Prolog queries from a GUI component.
- thread_monitor
- Open a graphical window indicating existing threads and their status.
- debug_monitor
- Open a graphical front-end for the library(debug)library 
that provides an overview of the topics and catches messages.
- xref
- Open a graphical front-end for the cross-referencer that provides an 
overview of predicates and their callers.