You may download 'loglog' module from here to enjoy testing Cube. This not mathematics module about 'log-log'. ;)
Loglog is the sample program which uses Delegate of XOOPS Cube layer. Loglog records when users do login or logout, and estimates how long users are staying in the site.
Read preload/Initialize.class.php. There are comments in English and Japanese. Delegate of XOOPS Cube is uniform procedure about callback. That's like function pointer at C, functor at C++, delegate of C# and D. You may understand directions of Delegate by reading the sample program.
Loglog is just sample program. But, if you hope more full-fledged logging module, do develop it! All of users welcome your act.