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From: cox@stpstn.UUCP (Brad Cox)
Newsgroups: comp.software-eng
Subject: Re: Reuse and Abstraction (was: reu
Message-ID: <5149@stpstn.UUCP>
Date: 2 Jun 90 16:17:48 GMT
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Reply-To: cox@stpstn.UUCP (Brad Cox)
Organization: Stepstone
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In article <19946@duke.cs.duke.edu> crm@romeo.UUCP (Charlie Martin) writes:
>The level of abstraction point is a good one, and is why we've mostly
>stopped writing machine language programs.  (There are only a few levels
>of abstraction where machine language is appropriate.)  But every time I
>try to get my hands on the modularity/binding technologies point, it
>falls apart and seems to turn into "putting things together from
>components."  If you have higher-level components it is easier, so long
>as the higher level componets are suited to what you are trying to do.
>
>I guess that sounds tautologous now.  Can you expand on your point a
>little?

The distinction is between "building from first principles" (fabrication)
and "building from components (assembly). Fabrication involves reuse of
only raw materials, while assembly involves reuse of higher-level components. 
The first involves a flat organizational structure (programming language 
vendors as providers of low-level raw materials; i.e. int, float, strcmp()), 
whereas the second involves a deep organizational structure; a software
components marketplace. Evolving from our present flat structure (cottage
industry) to a deep structure is what the IEEE paper means by a "software 
industrial revolution".

>On the gate-level vs higher-level point, I've used both Objective-C and
>C++ and I have to admit I didn't see much difference in the language
>per se.  There is/was a bigger library of higher level components to
>draw on, but then this is the result of longer and better funded
>development of these components.  

That is *precisely* my point. Viewing them as competing  *languages* misses
the fact one is solely a language and the other an *environment* of 
off-the-shelf software components (Software-ICs). 

>So is your second point that Objective-C is that much higher level than
>C++, and if so, on what basis?  Or is it that the bigger IC libraries
>gives OC the advantage.

It is "higher-level" in the sense that a soldering iron (for assembling chips
to make boards) is a higher-level tool than a photolithography machine (for
assembling gates to make blocks, and blocks to make chips). Both are
modularity/binding technologies, and both support reuse, but at radically
different *levels*. 

But soldering irons and photolithography machines *do not compete*, but
*support* each other. They provide *radically* different services to
*radically* different audiences. Photolithography machines require far
more skill to use than soldering irons (lower man-productivity) but deliver
greater performance (higher machine-productivity).  But it is the the
pluggability of soldering irons that created the very possibility of today's
marketplace in hardware components (by this I mean, it was the invention of
the silicon chip and circuit boards that made the very notion of a hardware
marketplace thinkable). So it is with Objective-C.

>I still don't see that OC is particularly advantageous compared to C++,
>but maybe that's a side issue.  In any case, it's your product and
>your idea, and you're entitiled to some pride of ownership: it really is
>a substantial thing.

Many people's difficulty here arises from comparing the technologies
themselves, rather than their organizational implications. In other
words photolithography machines are technologically impressive, rich 
functionality, need great skill to use well. Soldering irons are simple, 
and require much lower skill to use effectively. Compared as technologies,
photolithography machines are clearly 'superior'. But viewed insofar as 
their organizational implications, soldering irons created the very 
possibility of a multi-level marketplace in reusable hardware components. 
A *lot* more people are capable of using soldering irons than photolithography
machines.
-- 

Brad Cox; cox@stepstone.com; CI$ 71230,647; 203 426 1875
The Stepstone Corporation; 75 Glen Road; Sandy Hook CT 06482