-# However, because a `MClass` is global, it does not really have properties nor
-# belong to a hierarchy since the property and the
-# hierarchy of a class depends of a module.
+#
+# The drawback is that classes (`MClass`) contain almost nothing by themselves.
+# These do not really have properties nor belong to a hierarchy since the property and the
+# hierarchy of a class depends of the refinement in the modules.
+#
+# Most services on classes require the precision of a module, and no one can asks what are
+# the super-classes of a class nor what are properties of a class without precising what is
+# the module considered.
+#
+# For instance, during the typing of a source-file, the module considered is the module of the file.
+# eg. the question *is the method `foo` exists in the class `Bar`?* must be reformulated into
+# *is the method `foo` exists in the class `Bar` in the current module?*
+#
+# During some global analysis, the module considered may be the main module of the program.