[vos-d] s5 concurrency (design part 2)

[Peter Amstutz]

On Fri, Apr 06, 2007 at 05:16:16PM -0400, Reed Hedges wrote:

> There's also something called Flow-Based Programming that is similar. In
> some ways it's closer to VOS since Actors are, I think, more like method
> handlers (in VOS terminology). 

I don't agree.  Flow-based programming is very data-centric, in the 
sense that it views the system as a connected chain of inputs and 
outputs and black boxes doing transformations.  This is a good fit for 
certain kinds of data processing where data is streamed through a 
multistage system (audio/video processsing, certain types of batch 
processing) but isn't as useful for interactive systems.  If each box in 
a flow programming system is a vobject, and a connection between boxes 
means sending a message between vobjects, VOS starts out with the 
assumption that every box is potentially connected to every other box.  
At that point the flow model isn't particularly useful.

VOS grew out of my work in multiagent systems, and it's pretty well 
understood in that field that agents act independently of one another 
and their communication/coordination is asynchronous.  Thus, the idea 
that vobjects == actors seems like a natural fit.  You could say that 
the actor model is a design pattern that we happened to stumble upon, 
and that by recognizing it as such we can take advantage of the existing 
work on the topic.

> But "Actors Model" is more well known and more carefully studied and
> defined (though I guess we will be deviating from it)

Well, it's a model, not a precise specification.  The basic goal here is 
to define how flow-of-control works in a concurrent VOS application, in 
a way that is easy for users to grasp and prevents deadlocks and race 
conditions.

-- 
[   Peter Amstutz  ][ tetron at interreality.org ][ peter.amstutz at gdit.com ]
[Lead Programmer][Interreality Project][Virtual Reality for the Internet]
[ VOS: Next Generation Internet Communication][ http://interreality.org ]
[ http://interreality.org/~tetron ][ pgpkey:  pgpkeys.mit.edu  18C21DF7 ]

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