+# SPDX-License-Identifier: AGPL-3.0
+
+"""FUSE driver for Arvados Keep
+
+Architecture:
+
+There is one `Operations` object per mount point. It is the entry point for all
+read and write requests from the llfuse module.
+
+The operations object owns an `Inodes` object. The inodes object stores the
+mapping from numeric inode (used throughout the file system API to uniquely
+identify files) to the Python objects that implement files and directories.
+
+The `Inodes` object owns an `InodeCache` object. The inode cache records the
+memory footprint of file system objects and when they are last used. When the
+cache limit is exceeded, the least recently used objects are cleared.
+
+File system objects inherit from `fresh.FreshBase` which manages the object lifecycle.
+
+File objects inherit from `fusefile.File`. Key methods are `readfrom` and `writeto`
+which implement actual reads and writes.
+
+Directory objects inherit from `fusedir.Directory`. The directory object wraps
+a Python dict which stores the mapping from filenames to directory entries.
+Directory contents can be accessed through the Python operators such as `[]`
+and `in`. These methods automatically check if the directory is fresh (up to
+date) or stale (needs update) and will call `update` if necessary before
+returing a result.
+
+The general FUSE operation flow is as follows:
+
+- The request handler is called with either an inode or file handle that is the
+ subject of the operation.
+
+- Look up the inode using the Inodes table or the file handle in the
+ filehandles table to get the file system object.
+
+- For methods that alter files or directories, check that the operation is
+ valid and permitted using _check_writable().
+
+- Call the relevant method on the file system object.
+
+- Return the result.
+
+The FUSE driver supports the Arvados event bus. When an event is received for
+an object that is live in the inode cache, that object is immediately updated.
+
+"""