Hi Barend,
I do agree about a well-described structure for extensions. However, I'm not sure about all of this proposal. This completely separates the extensions from the libraries, even in releases. Indeed this will cost a lot of efforts in organization and maintanance.
Why not keep it like it is currently in GIL and in GGL (Boost.Geometry)? So instead of boost_extension at the root level, have it in .../boost/LIB/extensions and .../libs/LIB/test/extensions and .../libs/LIB/example/extensions (and probably the same for doc)? This way the (reviewed) extensions can be distributed within Boost and are automatically available for everybody. Besides that, the extensions are then kept together with the library they extend, which I would prefer.
Adding new code to accepted libraries would mean going through boost's review process.
The non reviewed extensions, and extensions-in-preparation, should live elsewhere, e.g. in the Sandbox, or maybe indeed at a specific Extension.Sandbox tree, or at an external resource (as GIL currently has)? Actually this is then like any Boost library in preparation.
Right now, I'm collecting gil extensions and trying to keep them alive but it's pretty unorganized.
Regards, Barend
Christian