Initial proof of concept

node.rb

@@ -0,0 +1,33 @@
+require 'rubygems'
+require 'eventmachine'
+
+class Node
+  attr_accessor :parent
+
+  def initialize(&strategy)
+    @children = []
+    @strategy = strategy
+  end
+
+  def <<(child)
+    child.parent = self
+    @children << child
+  end
+
+  def run
+    deferrable = @strategy.call
+    deferrable.callback do
+      puts "Strategy succeeded"
+      EM.next_tick(method(:run_children))
+    end
+    deferrable.errback do
+      puts "Strategy failed"
+    end
+  end
+
+  def run_children
+    @children.each do |child|
+      child.run
+    end
+  end
+end

test.rb

@@ -0,0 +1,31 @@
+require 'node'
+
+def create_deferrable(id)
+  deferrable = EM::DefaultDeferrable.new
+  deferrable.callback do
+    puts "Finished node #{id}"
+  end
+  EM::Timer.new(1) do
+    deferrable.succeed
+  end
+  deferrable
+end
+
+EM.run {
+  n1 = Node.new do
+    create_deferrable(1)
+  end
+
+  n2 = Node.new do
+    create_deferrable(2)
+  end
+
+  n3 = Node.new do
+    create_deferrable(3)
+  end
+
+  n1 << n2
+  n1 << n3
+
+  n1.run
+}