Path: utzoo!utgpu!water!watmath!clyde!rutgers!gatech!hao!noao!arizona!mike
From: mike@arizona.edu (Mike Coffin)
Newsgroups: comp.windows.misc
Subject: Re: Why I'm suspicious of NeWS
Message-ID: <3851@megaron.arizona.edu>
Date: 13 Feb 88 16:52:46 GMT
References: <2940@bloom-beacon.MIT.EDU>
Organization: U of Arizona CS Dept, Tucson
Lines: 45

From article <2940@bloom-beacon.MIT.EDU>, by martillo@athena.mit.edu (Yakim Martillo):
> The Xlib routines actually buffer up the messages to send to the
> remote until the process XFlush()'s them into the kernel for
> transmission.  Improperly coded X programs could probably generate
> zillions of little packets crossing the application kernel boundary
> but a competent coder would not write his routines that way.
> Incompetent NeWS programming could probably generate zillions of little
> NeWS programs for transmission.

Here's an extreme example, just to make a point.  Suppose we have a
main CPU in a robot on Mars, with a workstation on earth.  The
communication delay is on the order of minutes.  The robot detects an
anomalous situation, one that demands a decision from earth.  Two
scenarios:

	X) The robot pops up a menu on earth.  It pops up a cursor.  A
	   human moves the cursor to a selection.  Highlighting the
	   each selection takes several minutes, of course, because a
	   message has to be passed to Mars and back to accomplish it.
	   After three or four selections have been highlighted but
	   not picked, the mouse finally makes it to the correct one.
	   Then the human releases the mouse button; a couple minutes
	   later the robot knows what to do.

	NeWS)  The robot sends the entire menu selection program to
	   earth. The entire selection process takes place here, and a
	   single message is sent back.

Which interface would you rather use?  

Granted, most networks aren't that slow.  And for all I know, X11 has
menus built into the server, making the above scenario moot.  Even if
that has been done (has it?) it is just a special case; other kinds of
interaction will still force X programmers to use XFlush() to cross the
client/server boundary much more often than NeWS.  The bottom line is
that X needs to cross boundary every time visual feedback is needed,
unless a special case has been made and built into the X server.



-- 

Mike Coffin				mike@arizona.edu
Univ. of Ariz. Dept. of Comp. Sci.	{allegra,cmcl2,ihnp4}!arizona!mike
Tucson, AZ  85721			(602)621-4252