The X Window System is the default windowing technology for UNIX systems. It is also used on many other systems, if only as a way of accessing networked resources. Now, X is about to take on a whole new challenge: providing Web access to existing application software.

Let's say that Joe User is crawling around the Web, looking for information about CAD packages. He hits the NiftiCAD site, wades through NiftiCAD's marketing material, and ends up a page that offers free demonstrations. Nothing unusual so far.

The demonstration page, however, offers Broadway-based access to the NiftiCAD package. When Joe clicks on the demo link, the Broadway system goes into action. On Joe's machine, the browser loads a Broadway plug-in. On the NiftiCAD server, the HTTP Daemon starts up a copy of a demonstration program, linking its interactive I/O channels to Joe's session.

The demo program and Joe's Broadway plug-in communicate by means of X.fast, an optimized form of the X protocol. X.fast, formerly known as LBX (Low Bandwidth X), strips out much of the overhead that would normally be present in an X interchange. This allows the Broadway session to be reasonably crisp, even on typical (modem-based) Web links.

Because the Broadway interaction is based on X, the demonstration program is not limited to HTML's limited set of fonts, graphics, and widgets. Indeed, it can take advantage of the same features it would use with a local X-based user, including X-based audio support!

More critically, it can do so without any need for recoding. Making a demo program available over the Web is one thing; reworking its user interfaces into HTML or Java is quite another. By allowing existing applications to run over the Web, Broadway turns a virtual impossibility into a trivial exercise.

At this point, you may be wondering about security. What keeps Joe User (also known as Chris Cracker) from using the NiftiCAD program as a way to break into other parts of the server? To provide some peace of mind for the NiftiCAD sysadmin, Broadway provides a variety of security mechanisms:

Broadway security works with, and in addition to, existing Web security; it was designed for worldwide export, and requires no changes to applications. The Broadway security model is simple, dividing applications into two classes: Trusted and Untrusted. Trusted applications are applications inside your firewall gateway. Untrusted applications are outside the firewall. Broadway security prevents untrusted applications from stealing, destroying or modifying any trusted application's data.

The security system consists of three pieces. First, a small piece of code that runs in the corporate firewall. Second, security extensions in the Broadway server. And third, a security manager that works with the user to authorize exchanges between trusted and untrusted applications.

Nor is Broadway limited to X-based applications of UNIX servers. The server machine can run Windows, MacOS, or a mainframe OS; the application can be based on any of a variety of GUIs. On a Windows NT server, for instance, the X.fast communications code links up to the Graphics driver.

Broadway is intended to work with other Web-based facilities. Thus, a designer is free to select from a variety of client-server, remote execution, and compound document choices. Designers are encouraged to mix and match these choices; Broadway supports (or at least allows) them all.

Details

As of the beginning of 1997, the X Consortium (http://www.x.org/) will no longer have responsibility for the X Window System. That task, along with OSF (Mach, Motif, etc.) X/Open (POSIX, the UNIX trademark, etc.) and parts of the former Soviet Union, are being integrated into the Open Group (http://www.osf.org/).

The Open Group will continue and accelerate the convergence of X, Motif and the Common Desktop Environment (CDE) into a unified technology stack. The X Consortium expects to complete and release Broadway by the end of 1996:

Broadway, the code name for the next release of the X Window System, will be completed as planned by the end of the year, and will be made freely available to the public under the same terms as previous X Consortium releases. Broadway enables interactive UNIX and Windows applications to be integrated, unmodified, into HTML documents and published on World Wide Web servers, using plug-in technology, and includes network protocols for graphics and audio to provide remote access to those applications from inside Web browsers. The Broadway release is expected to be available from current sources, including worldwide ftp sites and CDROM distributors.