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we all have a solid grasp of the TV channel as a conduit for news, in formation and en tertainment. But the use of the channel metaphor has spun out of control and is becoming a source of confusion. There are now so many push vendors and many, if not most, are using a totally different definition of a channel. Of the four products we tested, each defines a channel differently:

For Microsoft Corp.'s Internet Explorer (IE) 4.0, a channel is a Web site that is crawled and accessed as a push channel under the direction of a Channel Definition Format (CDF) file. CDF is an implementation of the Extensible Markup Language (XML), which is itself a subset of the powerful, but complex, ISO Standard Generalized Markup Language (SGML). CDF is used to define a series of Web-based push channel components, including channel items, update schedules and abstracts. Web developers can easily create CDF files that tell Internet Explorer (IE) how to update and display a multilevel Web site as an IE 4.0 channel.

Netscape Communications Corp.'s Netcaster considers a channel any regularly crawled Web site that i s set up within Netcaster under "My Channels."

While users can set up any Web site as a Netcaster channel, Web developers who want some control over their channel within a client's Netcaster environment can use JavaScript 1.2 objects and methods. These tools provide automatic and tailored channel display configuration and update the schedule.

For BackWeb Technologies, a BackWeb channel is a single BackWeb Channel Server that feeds BackWeb Infopaks (scripted multimedia announcements with data) to BackWeb clients. A BackWeb Channel Server serves only one BackWeb channel, but it can organize a channel into subchannels and exposure groups. A content administrator manipulates these groups to vary the mix of Infopaks that are pushed to channel clients.

Marimba's Castanet uses the channel metaphor to denote a collection of files that makes up a single Java application, Java applet, Bongo Presentation or HTML source directory that is pushed by the Castanet Transmitter to the Castanet Tuner. A sin gle Castan et Transmitter can push many Castanet channels.

As you can see, the channel metaphor is getting a tremendous workout when it comes to new push products. Expect the confusion to persist until some market consolidation shakes out the channel metaphors that were never meant to be.