[Boost-users] Boost.Build Main vs. exe

There seem to be two different general approaches to using bjam. One is to use "objects" such as /Main/ and /Library/. This is described here: http://www.boost.org/tools/build/jam_src/Jamfile.html The other approach is to use "rules" such as /exe/ and /lib/. This is described here: http://www.boost.org/tools/build/v1/build_system.htm Am I correct in viewing these as separate approaches that I am free to choose between? Is one approach preferable to the other in terms of future compatability, or generally accepted practices? -- Regards, Steven