For example,CacheableData.fwd.hh and CacheableData.hh.What's the meaning of fwd?Help~~
They have to do with Rosetta's use of Owning Pointers for most/all Rosetta C++ objects. See the typedef in the fwd.hh file.
Why do you ask?
They're for C++ forward declarations. Basically, they're set up as separate files to make the code compile faster.
for more details.