The wrapper project

[Chris Pressey]

On Thu, 21 Aug 2003 11:06:54 +0200 (CEST)
Joe Armstrong <joe@REDACTED> wrote:

> 
>   I'm back .... (been on holiday)
> 
>   I've been thinking about stuff.
> 
>   Once upon a  time I was interested in "how to  program" I think that
> we now know  how to do this (not perfectly, but  adequately) - now I'm
> interested in "fitting things togther".
> 
>   I have convinced myself of the following:
> 
> 	1) Systems must be made of *isolated* components.
> 	2) The components must communicate by asynchronous message
> 	passing... (and a few more things which are not relevant to this
> 	discussion)
> 
>   Isolation is  the *essential* characteristic.  It means  that if one
> component crashes, the other components must not themselves crash.

See also: protected memory.
http://www.wikipedia.org/wiki/Protected_memory

> Two
> processes running on the same machine  should be as isolated as if one
> ran in (say) Sweden and the other in (say) the USA.
>
>   What these  process are written in  (language) and what  they run on
> (OS) is *irrelevant* - But the *protocol* between them is vital (hence
> my thoughts on UBF and the like (see www.sics.se/~joe/ubf).

Then the protocol becomes the OS, for all intents and purposes.

(And... you don't *really* believe that the choice of language is
"irrelevant", do you? :)

...

On Thu, 21 Aug 2003 17:04:03 +0200
Joachim Durchholz <joachim.durchholz@REDACTED> wrote:

> To keep the number of potential interactions down, Parnas propagated 
> "information hiding", cutting down on the number of interactions that
> a compiler will allow. (Information hiding is not intended to prevent 
> programmers from looking into components, its for preventing
> components from looking into other components.)

See also: the Law of Demeter.
http://www.ccs.neu.edu/home/lieber/LoD.html

-Chris