TITLE: It's Blueprints All The Way Down
AUTHOR: Eugene Wallingford
DATE: October 24, 2014  3:05 PM
DESC: 
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BODY:
Many people in and out of the software world think of design and
programming as separate activities, which is a natural result of
analogies that compare software development to engineering
disciplines.  I've never been fond of separating these tasks in
my mind.  When I build software with other people, there is too
much fluidity between designing software and writing code to
make separate roles productive.

In
<A HREF="http://khanlou.com/2014/10/the-myth-of-the-builder/">
   The Myth of the Builder</A>,
Soroush Khanlou objects to the analogy for a different reason:
designers and programmers are really doing the same sort of
thing, only at different levels of detail:

<BLOCKQUOTE><EM>
 ...  We know that the designer is not doing the building; if
 programmer is also not doing the building, how is software
 turning from idea into reality?
</EM></BLOCKQUOTE>

<BLOCKQUOTE><EM>
 What is happening is that the designer presents the software
 as very high-level blueprints to the programmer.  The
 programmer then takes those and creates a lower-level set of
 blueprints for the compiler.
</EM></BLOCKQUOTE>

Thinking in terms of blueprints at a higher or lower level helps
make sense of how it feels to be:
<UL>
<LI> designing software, and thinking about how this will play
     out code, and </LI>
<LI> writing code, and thinking about how this affects the
     design of the system. </LI>
</UL>

We can think of design and programming as different tasks, but
not really as different <EM>kinds</EM> of task.

Khanlou goes a step farther:

<BLOCKQUOTE><EM>
 (Incidentally, the compiler is producing an even lower-level
 blueprint, called the Intermediate Representation, which is
 translated in to a final set of blueprints, the specific
 instructions for different CPUs.  It's blueprints all the
 way down.)
</EM></BLOCKQUOTE>

That's a catchy phrase, with a nod to other parts of computing
culture.  (I first saw the phrase
<A HREF="http://en.wikipedia.org/wiki/Turtles_all_the_way_down">
   it's turtles all the way down</A>
in <EM>G&ouml;del, Escher, Bach</EM>, though I think its use in
computing goes back farther.)  Fortunately for software
developers and compiler writers, we eventually hit the bottom
turtle.  When we write most programs, we don't have to worry
about that, though.

Khanlou's blog ends with a useful reminder, echoing "Structure
and Interpretation of Computer Programs":

<BLOCKQUOTE><EM>
 It's not valuable to think of software as a bridge; it's too
 weird for that.
</EM></BLOCKQUOTE>

Analogies from software development to various engineering
disciplines can take us only so far.  Software is different.
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