The wrapper project

[Joachim Durchholz]

Joe Armstrong wrote:
> On Thu, 21 Aug 2003, Joachim Durchholz wrote:
>>Joe Armstrong wrote:
>>
>>>2) The components must communicate by asynchronous message passing
>>
>>I have an exception to consider:
>>When composing subcomponents from components,
> 
>   Uugh - do you mean the other way around?
> 
>   You make components from sub-components ... ????

You're right.
A bad case of one too many edits in a message...

>>*and* a crashing subcomponent shall crash the entire component,
>>*then* synchronous communication is appropriate.
> 
>   I assume you meant that
> 
>    1) components are made from sub-components
>    2) if a sub-component crashes you want the component to crash
> 
>   To do this (if that's what you meant) I would like asynchronous messages.
> 
>   The problem  with synchronous messages  is that you  can't implement
> them.  The laws  of physics preclude this. You need  to send a message
> between the  systems (which  even at the  speed of light  takes finite
> time) to  send information between the  systems - you  also change the
> state.

To give any sense to the moniker "asynchronous communication", you need 
to define something sensible for "synchronous communication".
Which, in my book, means that each request is guaranteed to be followed 
by a response, with no intermediate external activity of the server object.

Regards,
Jo