Actually, the trends I see point in the opposite direction.  Due to  
the unifying concepts of URLs and MIME, HTTP provides a convenient,  
portable, widely available tool for distributing and hyperlinking  
*any* sort of static or interactive information.  To the extent that  
HTML fails to fulfill needs, HTTP rather stands to gain in relative  
importance.
Two important examples of this trend on the horizon:
   * Several groups are working on HTTP-based hyper-TeX (really
      hyper-DVI) for distributing mathematical and scientific text.
   * WIRED is leading a discussion on HTTP-based distributed virtual
      reality.  A large number of commercial and academic groups have
      expressed interest in working on this.
As far as I can see, the pressures to move beyond HTTP and HTML are  
coming from different sources.  The server maintainers are the ones  
who are looking for new protocols beyond HTTP, while the browser  
authors are the ones looking for models of content beyond HTML.
These pressures aren't necessarily bad.  I agree that what makes the  
Web the Web -- what must remain constant in all these scenarios in  
order to hold the Web together -- is the hyperlink, the dynamic  
combination of:
   1. URI addressing,
   2. MIME typing, and
   3. link relationship values.
Naturally, it is also helpful if the number of protocols and content  
models is small, but I don't think that total unity is needed.
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Paul Burchard	<burchard@geom.umn.edu>
``I'm still learning how to count backwards from infinity...''
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