Following the instruction, I installed the SWI-Prolog (6.6.5 for MacOSX 10.6 and later) and xquartz (X11). After I downloaded the latest Eclipse version (both Kepler and Juno) and I installed the PDT plugin. The prolog console is not active and if I try to consult the .pl file nothing happens. Is there something I have not done?
Likely the PDT plug-in cannot find where SWI-Prolog is installed. Note that Mac OS X GUI applications don't run on top of the BSD layer and, as such, don't see any environment variables that you define there. The workaround is to define the necessary environment variables (e.g. pointing to the SWI-Prolog binary) in Eclipse itself.