From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2001-11-30T08:55:42+09:00
Subject: [ruby-talk:27002] Re: Can someone explain TupleSpaces?

In article <20011130002401.A2889@michael.neumann.all>,
Michael Neumann  <neumann@s-direktnet.de> wrote:
>Phil Tomson wrote:
>> 
>> First of all, what is the Tuple?  It seems to be a list of three items 
>> (though I've seen more in some of the lists) - is it a way of calling a 
>> method on a remote object by passing in an array of items with the first 
>> element being the name of the method? (that's the theory I came up with 
>> after looking at the examples - but I could be way off).
>
>Tuples come from mathematics. Unlike lists they have a predefined length. 
>For example (1,2,3) is a 3-tuple, (1,"string",:3,4) a quadruple etc.
>
>A TupleSpace is a place where you can store arbitrary tuples. 
>Two operations are defined on it:
>
>  - put a tuple into the TupleSpace
>  - get/remove a tuple (poss. specified by a pattern) from the TupleSpace
>  
>Both operations are performed atomic (thread-safe). 
>
>
>Suppose you have a server thread A and a client thread B. 
>
>Thread A calls the "get" method accepting tuples matching ("add",_,_)
>where _ is a placeholder for any value. Method "get" waits until a
>matching tuple appears in the TupleSpace. 
>
>The client thread B now wants to add two numbers. Therefore it puts a
>tuple ("add",2,3) into the TupleSpace. After that it waits for a tuple
>matching ("result",_).
>
>Now thread A returns from method "get", because a matching tuple
>("add",2,3) exists, and removes this tuple. In response it puts
>a tuple ("result", 5) back into the TupleSpace.
>
>Thread B gets now active again and removes the tuple ("result",5) from
>the TupleSpace. 
>
>> I guess I'm looking for the 50000ft view of TupleSpace... and can someone 
>> tell me why I would use them?
>
>With this architecture you can very easy communicate and synchronize
>between different
>threads or processes. 
>
>Regards,
>
>  Michael
>
Thanks.  It's starting to make sense.  I almost get the feeling that a 
TupleSpace is sort of like some kind of super Hash where keys and values 
are interchangable  only there can be multiple values and keys 
(well, it's probably a poor analogy.  I think I'm starting to see the 
light, though.)  

Phil