What is it?
The Filesystem Group Service uses directories and files with lists of entity keys (e.g., IDs) to model groups and their members in a group system. It's a quick way to get up and running and experimenting with groups.
Documentation
Read the uPortal Filesystem group service documentation, which includes a tutorial.
Possible Enhancements
We could use something like Commons VFS to put a layer between the Filesystem store and the underlying store. This could make it possible to use a wide range of sources, including zip files, ftp and webdav.