Multiuser Collaboration

While the ToolTalk and action mechanisms encourage cooperation between applications, the desktop also defines cross-user collaboration technologies. This means distributed access to shared user data. The desktop has defined some basic sharing mechanisms and has also built on top of existing mechanisms.

An example of building on an existing mechanism is the remote procedure call (RPC) client/service implementation of calendar management. The desktop provides a client-side library and API, RPC protocol, and daemon/service that enables users to share appointment information. (The API is being standardized through X.400 Application Programming Interface Association (XAPIA) to enable a cross-UNIX, PC, and palmtop calendar standard.) The RPC protocol enables a user to browse and directly edit another user's calendar. Access is controlled by a user-specific access control mechanism. Calendars are tied to hosts, and a calendar's data is maintained by a host-specific daemon. The desktop names calendars through a user@host format.

The Common Desktop Environment uses conventional distributed file systems to name files that are sharable on the network. To provide an interface that is independent of the distributed file system, the desktop provides an API to translate host-relative file names into locally expressible file names. Although the desktop is based on the NFS^TM system, it can be ported to run on top of other distributed file systems. Using the desktop file-name mapping API, an opaque file name object can be constructed and passed between desktop clients across the network and resolved in a host-specific way. Also, to simplify the programming task and end user metaphor, Common Desktop Environment applications should present remote file references as local file paths.

One of the fundamentals of building multiuser collaboration applications is the ability to share files. The conventions for naming network files, in conjunction with a ToolTalk file-sharing mechanism called file scoping, enable multiuser collaboration through file sharing. File scoping is more than a mechanism for simple, exclusive access control. Cooperating clients can use file-scope access to negotiate for access to files. For example, an application that has exclusive access to a file could ask whether the user was done with the file when another application wanted to gain exclusive access to the file.