TODO: See the developer API documentation and the EntityFS source code until this is written. TODO: entity implementations should be designed to be proxied TODO: entity adapter implementations should be designed to be proxied TODO: how is copy implemented? TODO: layer image from architecture overview TODO: entity implementation layer generic file system implementation TODO: backend implementation layer backend specific TODO: entity implementation layer handles synchronization. No locking in backend implementation layer. TODO: a consequence of proxying is that entity objects (or entity adapter objects for that matter) never should be cast to a specific implementation. TODO: responsibilities for file system implementation layer: * no write access to read only entities * locking * access controls * etc. TODO: entity implementation proxy stack, entity adapter proxy stack. TODO: for existing implementations, the source code is the authoritative documentation