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Summary of SpecialK

The core broker is expressed as a parametrically polymorphic pattern using delimited continuations in monadic style to match consumers to producers. Some of the features that come out of this architecture are

• typed messaging that aligns perfectly with π-calculus style sorts
• huge range of messaging styles from pub/sub to queue'd to join patterns all expressed in one neat package
• scaling -- initial performance tests suggests this has nice scaling properties -- though this hasn't been properly stressed

The current architecture looks like this

/ XMLDB                                                             XMLDB \

kvdb kvdb
\ RabbitMQClient <-> RabbitMQBroker <-> RabbitMQBroker <-> RabbitMQClient /

XQuery/docs/diagrams/SpecialKGetFlow.pdf

with the kvdb providing an in-memory cache with the core broker as described above.

The programming API for this is incredibly simple. A programmer writes

reset{  // mark the boundary of the delimited continuation
   for( 
     event1 <- kvdb.get( <PrologTerm1> ); // get the stream of events matching pattern1
     ... ; 
     eventK <- kvdb.get( <PrologTermK> ) // get the stream of events matching patternK
     if filter( event1, ..., eventK ) // only call the continuation below if events meet a condition
   ) {
       // complex event handling code goes here
       ...
   }
}

All the threading, session management, etc is handled behind this API -- which effects a join pattern.