Re: Mars Rover Controlled By Java

From: Harry Conover (hhc314_at_yahoo.com)
Date: 01/24/04 

Date: 23 Jan 2004 19:29:42 -0800

"Michael N. Christoff" <mchristoff@sympatico.caREMOVETHIS> wrote in message news:<6bFPb.16559$cQ6.521869@news20.bellglobal.com>...
> > > Java is certainly not a member of this tight-knit
> > > club of system implementation languages, and I simply cannot picture
> > > anyone even attempting to implement a real-time OS using it.
> > >
>
> As I mentioned, you would not implement the OS in Java, but would implement
> a VM for the OS that allows one to run Java code with deterministic time
> contraints on operations.

No, what you actually posted was (unless attrition of this to you was
in error):

"> > Java, the software developed by Sun Microsystems in the mid-1990s
as a
> > universal operating system for Internet applications, gave NASA a low-cost
> > and easy-to-use option for running Spirit, the robotic rover that rolled
> > onto the planet's surface on Thursday in search of signs of water and life."

Running Java code with deterministic time constraint on operations
could be conceptually employed to construct a real-time OS, but in
reality could not be done simply due to the fact that the Java
implementation is so layered and ridiculously bloated, that it would
be practically incapable of meeting the microsecond and millisecond
timing constraints typically imposed on the deep end of a real-time
operating systems.

Certainly Java is capable of non real-time task such as the timely
update of a wall clock time display, or the issuance of coontrol
sequences based on clock time, but it depends of the capabilities of
some RTOS to provide the time-of-day services on which it feed to
provide these capabilities.

Due to it's very high-order application focus (that it, consists of
application level functions, not machine oriented instructions), I
really cannot imagine of a Java implementation that would lend itself
to RTOS applications, whether a VM implementation or not.

Then too, I don't believe that this is what you are trying to say, and
I believe the confusion is cause by someone erroneously attributed a
quote from the Sun PR blurb to you.

I suspect that tranlated to my language, what you're telling us is
that one could employ a Java implementation running on top of the
environment created by a real-time operating system, something that is
routinely done.

I have no problem with Java, its capabilities, or its applications,
however I do strenuously object to the statement that: "Java, the
software developed by Sun Microsystems in the mid-1990s as universal
operating system for Internet applications, gave NASA a low-cost and
easy-to-use option for running Spirit, the robotic rover that rolled
onto the planet's surface on Thursday in search of signs of water and
life."

The simple facts of life are that Java was not developed as a
"universal operating system for Internet applications" nor is a
real-time operating system "option for running Spirit".

Spirit's applications level software could well be Java, or Fortran,
Basic, Jovial, Lisp, Forth (Ghod Forbid), or just about any HOL. My
point is that you can damn't well bet that the RTOS that directly
controls (both the good and now the bad on Spirit) is very likely
programmed in a language providing direct machine instruction level
control of its processor, likely C, C++, or assemly langage just as is
the embedded bios in your computer, RAID server, or network
controller.

Fact is, the controller aboard Spirit is functioning as simply a
glorified PLC, and likely has very similar embedded firmware to that
of earthborne PLCs. Why wouldn't JPL copy this model, 90% of man's
controller experience is using PLCs.

Rant complete! ... -.-

                                                    Harry C.

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