From: kr%portal@cup.portal.com
Newsgroups: sci.nanotech
Subject: Re: Definitions
Date: 8 Sep 92 20:33:16 GMT

In order to add to the confusion in terminology, I would like to suggest
somewhat different definitions. (Of course, I hope not to confuse further
but to hopefully clarify a bit.)

In responding to a comment by JoSH:

->> ... I suggest using "proto-assembler" to refer
->> to macroscopic devices able to controlled molecular construction,
->> but not able to replicate themselves, and "assembler" to mean
->> the self-reproducing kind given that name by Drexler.
->> --JoSH]
,
willdye@helios.unl.edu (Will Dye) defines in
<11654.3.744.1 Definitions>(9/2/92)

->Assembler: Big programmable molecule for molecular manipulation.
->Can be programmed to replicate itself.
->
->Replicator: Big non-programmable molecule that self-replicates.
->
->Proto-assembler: Bulk device that can manipulate molecules, but 
->can't (within practicality) self-replicate.

"Bulk device" was presumably meant to be a "bulky device". Usually in the
terminology of chemistry, bulk means a large number of small (molecular)
entities, like in "bulk solvent".
A replicator need not be a "big" molecule. If the only task is to self-
replicate, then small and dumb molecules as investigated by von Kiedrowski 
and Rebek demonstrate the principle. But obviously, pure self-replication
in itself is not terribly interesting.
The much more interesting goal is to go after Universal Constructors
(in the sense of von Neumann) which are capable of producing whatever can be
programmed, thus including more copies of itself, if programmed to do so.
Then we have a "Replicator" which can do something interesting beyond (but
including) mere self-replication. This device can be called "Assembler".
But in molecular manufacturing, there are assemblers of different flavors.
An Assembler is basically a piece of machinery that can assemble something
else, very much like a piece of machinery in a conventional factory. Only
in rare exceptional cases will such an Assembler have to be Universal, 
meaning that it can produce _anything_, including copies of itself. Most
of the assembly power will be needed in dumb, repetitive assembly-line
processes.
Of the Universal Assemblers there are then at least two different kinds:
the self-contained and the non-self-contained. The self-contained ones
will contain the instructions for self-replication in an on-board
control-computer. This then would be the much alluded-to "true Drexlerian-
style Assembler".
But there is a cruder version of self-replication (which might not be as
theoretically elegant as the completely self-contained version but is a lot
more practical). To simplify the process of bootstrapping nanotech, one will
want to construct the most minimalistic stripped-down bare-bone version of
useful self-replication with which one can get away with, which mainly means
throwing the control-computer off-board. The goal is to build some complex
molecular device that is capable of receiving commands from the macroscopic
world (generated by a macroscopic computer) and which can follow these
assembly-instructions to put together building-block-molecules in the proper
sequence. I would call such a device a "crude Proto-Assembler". It already
has certain important characteristics of a "true assembler", like the capability
of universal assembly (universal within the restrictions of the limited
"alphabet" of building-blocks) and so the capability to self-reproduce. (Note
that this crude version of self-replication is similar to PCR, in which a piece
of DNA "self-replicates", but not in a self-contained and fully automatic
fashion, but only with supplying an external control input in the form
of temperature-cycling.) But such an early-stage crude Proto-Assembler will be
built from non-ideal materials (strange molecules instead of diamond) and
will always be connected by an information-navel to the macroscopic world.
If you cut off the stream of commands, the assembler will stop working.
A Proto-Assembler could be built using a macroscopic device, a derivative
of an AFM. Such a device could be called a "Molecular Manipulator" and it
allows the positioning of molecules to effect chemical reactions in a
precisely definable way.
If the same building-block-molecules are used for constructing with the
Molecular Manipulator as the crude Proto-Assembler (which is being constructed)
is capable of handling, then self-replication could be invoked right away to
produce more of these valuable Proto-Assembler devices. The whole deal of
crunching down on the problem of bootstrapping nanotech focusses
on using non-trivial self-replication as soon as possible. So I don't see
that many intermediate stages of "useful" products because the development will
go forward fairly rapidly after the first hurdle has been taken. Producing
diamond-fibers with a non-mature nanotechnology, as has been suggested for
intermediary applications, will be difficult to achieve because diamond is
about the most difficult material that one can synthesize. It probably
requires very reactive carbon radicals and carbenes and stuff, operating under
a local high-vacuum, and so requires fairly capable assemblers. It probably
will be best to move straight ahead to the more advanced assemblers without
pausing a lot at the intermediary stages. There is no point in wasting time
if fierce competition is going to race by to the left and to the right. 

To summarize this:
In the world as I can see it, there are macroscopic Molecular Manipulators
(MMM or M3 ? (just a joke :-)) which can be used to construct crude Proto-
Assemblers which go on to construct more refined Assemblers through a few
generations until high quality molecular manufacturing is implemented, using
powerful, diamondoid Assemblers of which only the smallest fraction will be
Universal.



------- End - of - Message -----------------------
(responsibility for my personal opinions is mine)

Richard Stallman : "The more society becomes
        information instead of material objects,
        this question of whether
        a person can copy things
        will make the difference between

        a world of universal prosperity
     or a world of constant rat race."

__________________________________________________
kr@cup.portal.com            IIIII  M   M  M   M
Markus Krummenacker            I    MM MM  MM MM
(working for                   I    M M M  M M M
 The Institute for             I    M   M  M   M
 Molecular Manufacturing)      I    M   M  M   M
                             IIIII  M   M  M   M