&fml8; provides a boot loader to resolve version dependence dynamically. For example, the loader boot straps &fml8; as follows: fml (libexec/distribute) boots like this ... functions class ---------------------------------------- main::Bootstrap() libexec/loader | V main::Bootstrap2() FML::Process::Switch | V ProcessSwitch() FML::Process::Switch | | | switch to ($obj = FML::Process:Distribute) | V ProcessStart($obj,$args) FML::Process::Flow &fml8; loader boot straps like this in the case of distribution. /usr/local/libexec/fml/distributre (is same as /usr/local/libexec/fml/loader in fact) reads /usr/local/etc/fml/main.cf and resolvers the version it should use from $fml_version variable. Let $fml_version current-20010501. The loader uses library perl modules under /usr/local/lib/fml/current-20010501/. The loader resets @INC (perl include path). It loads FML::Process::Switch and checks $0 (program name in process table). The loader resolves from the name that the role is distribution. It loads FML::Process::Distribute and switches to the class. The relation between program name and class (perl module) is defined at /usr/local/etc/fml/defaults/$fml_version/modules file. FML::Process::Flow::ProcessStart() function drives these sequential steps. ProcessStart() takes FML::Process::Distribute object as an argument and drives the object. FML::Process::Distribute >-| FML::Process::Command >-|-- FML::Process::Kernel FML::Process::Mead >-| | |-use-a FML::Parse |-use-a FML::Config |-use-a FML::Log |-use-a ... SOMETHING ... libexec/loader (wrapper): executes Bootstrap() runction. libexec/distribute et.al. is a symlink(2) to this loader. See under /usr/local/libexec/fml/ path. reads /usr/local/etc/fml/main.cf and resolves $fml_version. reset @INC by main.cf value. Since default_config.cf is version dependent, the loader should evaluate the file before it reads ML specific configuration files. Evaluate @ARGV and resolves which ML specific configuration files we need to load. load FML::Process::Switch class which is also version dependent. The loader executes Bootstrap2() and ProcessSwitch() to switch the context to each one such as distribution, command mail et.al. In this time, the loader knows the role from $0 process name. Exapmle of Polymorphyism: dynamic binding of module and creation of process object in starting the process. FML::Process::Flow describes the flow of process like this: $process = new FML::Process::SOMETHING; $process->prepare($args); $process->verify_request($args); $process->run($args); $process->finish($args); Each process should probide proper methods under FML::Process:: class. Currently &fml8; resolves them in prepare() under FML::Process:: classes. Here is a part of background idea. main::Bootstrap() resoles $fml_version based on main.cf information. pass hints to some processes e.g. CGI. CGI only it should ignore invalid input. $ml_name $and ml_domain is hard-coded in cgi scripts. main::Bootstrap2() ProcessSwitch() resolves the module, configuration files, library path and @INC. pass hints to some processes e.g. CGI. CGI only ProcessStart($obj, $args) main process starts new prepare resoles $ml_name and $ml_domain. parse input from CGI using hints. determine ml specific configuration files. parse incoming message. parse command line arguments.